diff --git a/Apollo.xcodeproj/project.pbxproj b/Apollo.xcodeproj/project.pbxproj
index c69e84c543..81b6a308ce 100644
--- a/Apollo.xcodeproj/project.pbxproj
+++ b/Apollo.xcodeproj/project.pbxproj
@@ -180,7 +180,7 @@
 		DE05860B266978A100265760 /* SelectionSet.swift in Sources */ = {isa = PBXBuildFile; fileRef = DE3C7B10260A6FC900D2F4FF /* SelectionSet.swift */; };
 		DE05860C266978A100265760 /* FragmentProtocols.swift in Sources */ = {isa = PBXBuildFile; fileRef = DE3C7B12260A6FC900D2F4FF /* FragmentProtocols.swift */; };
 		DE05860D266978A100265760 /* ScalarTypes.swift in Sources */ = {isa = PBXBuildFile; fileRef = DE3C7B15260A6FCA00D2F4FF /* ScalarTypes.swift */; };
-		DE05860E266978A100265760 /* GraphQLOptional.swift in Sources */ = {isa = PBXBuildFile; fileRef = 9B68F06E241C649E00E97318 /* GraphQLOptional.swift */; };
+		DE05860E266978A100265760 /* GraphQLNullable.swift in Sources */ = {isa = PBXBuildFile; fileRef = 9B68F06E241C649E00E97318 /* GraphQLNullable.swift */; };
 		DE058610266978A100265760 /* InputValue.swift in Sources */ = {isa = PBXBuildFile; fileRef = 9FC9A9C11E2D3CAF0023C4D5 /* InputValue.swift */; };
 		DE058616266978A100265760 /* GraphQLEnum.swift in Sources */ = {isa = PBXBuildFile; fileRef = DE3C7B14260A6FCA00D2F4FF /* GraphQLEnum.swift */; };
 		DE05862D2669800000265760 /* Matchable.swift in Sources */ = {isa = PBXBuildFile; fileRef = 9BE071AE2368D34D00FA5952 /* Matchable.swift */; };
@@ -226,7 +226,6 @@
 		DE674D9D261CEEE4000E8FC8 /* c.txt in Resources */ = {isa = PBXBuildFile; fileRef = 9B2061172591B3550020D1E0 /* c.txt */; };
 		DE674D9E261CEEE4000E8FC8 /* b.txt in Resources */ = {isa = PBXBuildFile; fileRef = 9B2061182591B3550020D1E0 /* b.txt */; };
 		DE674D9F261CEEE4000E8FC8 /* a.txt in Resources */ = {isa = PBXBuildFile; fileRef = 9B2061192591B3550020D1E0 /* a.txt */; };
-		DE6B156A261505660068D642 /* GraphQLMap.swift in Sources */ = {isa = PBXBuildFile; fileRef = DE6B154A261505450068D642 /* GraphQLMap.swift */; };
 		DE6B15AF26152BE10068D642 /* DefaultInterceptorProviderIntegrationTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = DE6B15AE26152BE10068D642 /* DefaultInterceptorProviderIntegrationTests.swift */; };
 		DE6B15B126152BE10068D642 /* Apollo.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = 9FC750441D2A532C00458D91 /* Apollo.framework */; };
 		DE736F4626FA6EE6007187F2 /* InflectorKit in Frameworks */ = {isa = PBXBuildFile; productRef = E6E4209126A7DF4200B82624 /* InflectorKit */; };
@@ -627,7 +626,7 @@
 		9B68353E2463481A00337AE6 /* ApolloUtils.framework */ = {isa = PBXFileReference; explicitFileType = wrapper.framework; includeInIndex = 0; path = ApolloUtils.framework; sourceTree = BUILT_PRODUCTS_DIR; };
 		9B68354A2463498D00337AE6 /* Apollo-Target-ApolloUtils.xcconfig */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = text.xcconfig; path = "Apollo-Target-ApolloUtils.xcconfig"; sourceTree = "<group>"; };
 		9B68F0542416B33300E97318 /* LineByLineComparison.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = LineByLineComparison.swift; sourceTree = "<group>"; };
-		9B68F06E241C649E00E97318 /* GraphQLOptional.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = GraphQLOptional.swift; sourceTree = "<group>"; };
+		9B68F06E241C649E00E97318 /* GraphQLNullable.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = GraphQLNullable.swift; sourceTree = "<group>"; };
 		9B6CB23D238077B60007259D /* Atomic.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = Atomic.swift; sourceTree = "<group>"; };
 		9B708AAC2305884500604A11 /* ApolloClientProtocol.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = ApolloClientProtocol.swift; sourceTree = "<group>"; };
 		9B74BCBE2333F4ED00508F84 /* run-bundled-codegen.sh */ = {isa = PBXFileReference; lastKnownFileType = text.script.sh; name = "run-bundled-codegen.sh"; path = "scripts/run-bundled-codegen.sh"; sourceTree = SOURCE_ROOT; };
@@ -853,7 +852,6 @@
 		DE5EB9C626EFE0F80004176A /* JSONValueMatcher.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = JSONValueMatcher.swift; sourceTree = "<group>"; };
 		DE5EB9CA26EFE5510004176A /* MockOperation.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = MockOperation.swift; sourceTree = "<group>"; };
 		DE664ED326602AF60054DB4F /* Selection.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = Selection.swift; sourceTree = "<group>"; };
-		DE6B154A261505450068D642 /* GraphQLMap.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = GraphQLMap.swift; sourceTree = "<group>"; };
 		DE6B15AC26152BE10068D642 /* ApolloServerIntegrationTests.xctest */ = {isa = PBXFileReference; explicitFileType = wrapper.cfbundle; includeInIndex = 0; path = ApolloServerIntegrationTests.xctest; sourceTree = BUILT_PRODUCTS_DIR; };
 		DE6B15AE26152BE10068D642 /* DefaultInterceptorProviderIntegrationTests.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = DefaultInterceptorProviderIntegrationTests.swift; sourceTree = "<group>"; };
 		DE6B15B026152BE10068D642 /* Info.plist */ = {isa = PBXFileReference; lastKnownFileType = text.plist.xml; path = Info.plist; sourceTree = "<group>"; };
@@ -1492,7 +1490,6 @@
 			children = (
 				DE9C04AB26EA763E00EC35E7 /* Accumulators */,
 				9FF90A5C1DDDEB100034C3B6 /* GraphQLExecutor.swift */,
-				DE6B154A261505450068D642 /* GraphQLMap.swift */,
 				9FA6F3671E65DF4700BF8D73 /* GraphQLResultAccumulator.swift */,
 				9F7BA89822927A3700999B3B /* ResponsePath.swift */,
 				DE0586322669948500265760 /* InputValue+Evaluation.swift */,
@@ -1729,7 +1726,7 @@
 				DE2FCF2226E8082A0057EA67 /* SchemaTypes */,
 				DE2FCF1E26E807CC0057EA67 /* CacheTransaction.swift */,
 				DE9C04AE26EAAEE800EC35E7 /* CacheReference.swift */,
-				9B68F06E241C649E00E97318 /* GraphQLOptional.swift */,
+				9B68F06E241C649E00E97318 /* GraphQLNullable.swift */,
 				DE3C7B12260A6FC900D2F4FF /* FragmentProtocols.swift */,
 				DE3C7B14260A6FCA00D2F4FF /* GraphQLEnum.swift */,
 				DE3C7B11260A6FC900D2F4FF /* ResponseDict.swift */,
@@ -2828,7 +2825,6 @@
 				9FEB050D1DB5732300DA3B44 /* JSONSerializationFormat.swift in Sources */,
 				9B260BEB245A020300562176 /* ApolloInterceptor.swift in Sources */,
 				54DDB0921EA045870009DD99 /* InMemoryNormalizedCache.swift in Sources */,
-				DE6B156A261505660068D642 /* GraphQLMap.swift in Sources */,
 				9B554CC4247DC29A002F452A /* TaskData.swift in Sources */,
 				9B9BBAF524DB4F890021C30F /* AutomaticPersistedQueryInterceptor.swift in Sources */,
 				9BA1244A22D8A8EA00BF1D24 /* JSONSerialization+Sorting.swift in Sources */,
@@ -2946,7 +2942,7 @@
 				DE2FCF2A26E8083A0057EA67 /* Field.swift in Sources */,
 				DE05860D266978A100265760 /* ScalarTypes.swift in Sources */,
 				DE9C04AF26EAAEE800EC35E7 /* CacheReference.swift in Sources */,
-				DE05860E266978A100265760 /* GraphQLOptional.swift in Sources */,
+				DE05860E266978A100265760 /* GraphQLNullable.swift in Sources */,
 				DECD53CF26EC0EE50059A639 /* OutputTypeConvertible.swift in Sources */,
 				DE2FCF2126E807EF0057EA67 /* Cacheable.swift in Sources */,
 				DEA6A83426F298660091AF8A /* ParentType.swift in Sources */,
diff --git a/Sources/Apollo/ApolloStore.swift b/Sources/Apollo/ApolloStore.swift
index dcbce0268b..9ba8df7433 100644
--- a/Sources/Apollo/ApolloStore.swift
+++ b/Sources/Apollo/ApolloStore.swift
@@ -184,7 +184,7 @@ public class ApolloStore {
     public func readObject<SelectionSet: RootSelectionSet>(
       ofType type: SelectionSet.Type,
       withKey key: CacheKey,
-      variables: [String: InputValue]? = nil
+      variables: GraphQLOperation.Variables? = nil
     ) throws -> SelectionSet {
       return try self.readObject(ofType: type,
                                  withKey: key,
@@ -195,7 +195,7 @@ public class ApolloStore {
     func readObject<SelectionSet: RootSelectionSet, Accumulator: GraphQLResultAccumulator>(
       ofType type: SelectionSet.Type,
       withKey key: CacheKey,
-      variables: [String: InputValue]? = nil,
+      variables: GraphQLOperation.Variables? = nil,
       accumulator: Accumulator
     ) throws -> Accumulator.FinalResult {
       let object = try loadObject(forKey: key).get()
diff --git a/Sources/Apollo/GraphQLExecutor.swift b/Sources/Apollo/GraphQLExecutor.swift
index d6ca712eaa..9b70e64cb1 100644
--- a/Sources/Apollo/GraphQLExecutor.swift
+++ b/Sources/Apollo/GraphQLExecutor.swift
@@ -15,13 +15,13 @@ typealias GraphQLFieldResolver = (_ object: JSONObject, _ info: FieldExecutionIn
 typealias ReferenceResolver = (CacheReference) -> PossiblyDeferred<JSONObject>
 
 struct ObjectExecutionInfo {
-  let variables: [String: InputValue]?
+  let variables: GraphQLOperation.Variables?
   let schema: SchemaConfiguration.Type
   private(set) var responsePath: ResponsePath = []
   private(set) var cachePath: ResponsePath = []
 
   fileprivate init(
-    variables: [String: InputValue]?,
+    variables: GraphQLOperation.Variables?,
     schema: SchemaConfiguration.Type,
     responsePath: ResponsePath,
     cachePath: ResponsePath
@@ -33,7 +33,7 @@ struct ObjectExecutionInfo {
   }
 
   fileprivate init(
-    variables: [String: InputValue]?,
+    variables: GraphQLOperation.Variables?,
     schema: SchemaConfiguration.Type,
     withRootCacheReference root: CacheReference? = nil
   ) {
@@ -173,7 +173,7 @@ final class GraphQLExecutor {
     selectionSet: RootSelectionSet.Type,
     on data: JSONObject,
     withRootCacheReference root: CacheReference? = nil,
-    variables: [String: InputValue]? = nil,
+    variables: GraphQLOperation.Variables? = nil,
     accumulator: Accumulator
   ) throws -> Accumulator.FinalResult {
     let info = ObjectExecutionInfo(variables: variables,
@@ -247,8 +247,7 @@ final class GraphQLExecutor {
         groupedFields.append(field: field, withInfo: info)
 
       case let .booleanCondition(booleanCondition):
-        guard case let .scalar(boolValue as Bool) =
-                info.variables?[booleanCondition.variableName] else {
+        guard let boolValue = info.variables?[booleanCondition.variableName] as? Bool else {
           throw GraphQLError("Variable \"\(booleanCondition.variableName)\" was not provided.")
         }
         if boolValue == !booleanCondition.inverted {
diff --git a/Sources/Apollo/GraphQLGETTransformer.swift b/Sources/Apollo/GraphQLGETTransformer.swift
index 5108f1effd..97bd29c031 100644
--- a/Sources/Apollo/GraphQLGETTransformer.swift
+++ b/Sources/Apollo/GraphQLGETTransformer.swift
@@ -1,19 +1,20 @@
 import Foundation
 #if !COCOAPODS
 import ApolloUtils
+import ApolloAPI
 #endif
 
 public struct GraphQLGETTransformer {
 
-  let body: GraphQLMap
+  let body: JSONEncodableDictionary
   let url: URL
 
-  /// A helper for transforming a GraphQLMap that can be sent with a `POST` request into a URL with query parameters for a `GET` request.
+  /// A helper for transforming a `JSONEncodableDictionary` that can be sent with a `POST` request into a URL with query parameters for a `GET` request.
   ///
   /// - Parameters:
-  ///   - body: The GraphQLMap to transform from the body of a `POST` request
+  ///   - body: The `JSONEncodableDictionary` to transform from the body of a `POST` request
   ///   - url: The base url to append the query to.
-  public init(body: GraphQLMap, url: URL) {
+  public init(body: JSONEncodableDictionary, url: URL) {
     self.body = body
     self.url = url
   }
@@ -30,7 +31,7 @@ public struct GraphQLGETTransformer {
 
     do {
       _ = try self.body.sorted(by: {$0.key < $1.key}).compactMap({ arg in
-        if let value = arg.value as? GraphQLMap {
+        if let value = arg.value as? JSONEncodableDictionary {
           let data = try JSONSerialization.sortedData(withJSONObject: value.jsonValue)
           if let string = String(data: data, encoding: .utf8) {
             queryItems.append(URLQueryItem(name: arg.key, value: string))
diff --git a/Sources/Apollo/GraphQLMap.swift b/Sources/Apollo/GraphQLMap.swift
deleted file mode 100644
index 4c2cd3549f..0000000000
--- a/Sources/Apollo/GraphQLMap.swift
+++ /dev/null
@@ -1,22 +0,0 @@
-#if !COCOAPODS
-import ApolloAPI
-#endif
-
-#warning("TODO: Delete?")
-public typealias GraphQLMap = [String: JSONEncodable?]
-
-fileprivate extension Dictionary where Key == String, Value == JSONEncodable? {
-  var withNilValuesRemoved: Dictionary<String, JSONEncodable> {
-    filter { $0.value != nil }
-  }
-}
-
-public protocol GraphQLMapConvertible: JSONEncodable {
-  var graphQLMap: GraphQLMap { get }
-}
-
-public extension GraphQLMapConvertible {
-  var jsonValue: JSONValue {
-    return graphQLMap.withNilValuesRemoved.jsonValue
-  }
-}
diff --git a/Sources/Apollo/GraphQLResponse.swift b/Sources/Apollo/GraphQLResponse.swift
index ce55388594..bc57ff5541 100644
--- a/Sources/Apollo/GraphQLResponse.swift
+++ b/Sources/Apollo/GraphQLResponse.swift
@@ -8,7 +8,7 @@ public final class GraphQLResponse<Data: RootSelectionSet> {
   public let body: JSONObject
 
   private let rootKey: CacheReference
-  private let variables: [String: InputValue]?
+  private let variables: GraphQLOperation.Variables?
 
   public init<Operation: GraphQLOperation>(operation: Operation, body: JSONObject) where Operation.Data == Data {
     self.body = body
diff --git a/Sources/Apollo/InputValue+Evaluation.swift b/Sources/Apollo/InputValue+Evaluation.swift
index 055175f3de..f233c837b2 100644
--- a/Sources/Apollo/InputValue+Evaluation.swift
+++ b/Sources/Apollo/InputValue+Evaluation.swift
@@ -4,12 +4,12 @@ import ApolloAPI
 import Foundation
 
 extension Selection.Field {
-  func cacheKey(with variables: [String: InputValue]?) throws -> String {
-    if
-      let argumentValues = try arguments?.evaluate(with: variables),
-      argumentValues.apollo.isNotEmpty {
-        let argumentsKey = orderIndependentKey(for: argumentValues)
-        return "\(name)(\(argumentsKey))"
+  func cacheKey(with variables: GraphQLOperation.Variables?) throws -> String {
+    if let arguments = arguments,
+       case let argumentValues = try InputValue.evaluate(arguments, with: variables),
+       argumentValues.apollo.isNotEmpty {
+      let argumentsKey = orderIndependentKey(for: argumentValues)
+      return "\(name)(\(argumentsKey))"
     } else {
       return name
     }
@@ -17,67 +17,54 @@ extension Selection.Field {
 
   private func orderIndependentKey(for object: JSONObject) -> String {
     return object.sorted { $0.key < $1.key }.map {
-      if let object = $0.value as? JSONObject {
+      switch $0.value {
+      case let object as JSONObject:
         return "[\($0.key):\(orderIndependentKey(for: object))]"
-      } else if let array = $0.value as? [JSONObject] {
+      case let array as [JSONObject]:
         return "\($0.key):[\(array.map { orderIndependentKey(for: $0) }.joined(separator: ","))]"
-      } else {
+      case is NSNull:
+        return "\($0.key):null"
+      default:
         return "\($0.key):\($0.value)"
       }
     }.joined(separator: ",")
   }
 }
 
-extension Selection.Field.Arguments {
-
-  func evaluate(with variables: [String: InputValue]?) throws -> JSONObject {
-    /// `Selection.Field.Arguments` can only ever hold arguments of `.object` type. Which will
-    /// always resolve to an `.object` value. So force casting to `JSONObject` is safe.
-    return try arguments.evaluate(with: variables) as! JSONObject
-  }
-}
-
 extension InputValue {
-  func evaluate(with variables: [String: InputValue]?) throws -> JSONValue {
+  private func evaluate(with variables: GraphQLOperation.Variables?) throws -> JSONValue? {
     switch self {
-    case let .scalar(value):
-      return value
-
     case let .variable(name):
       guard let value = variables?[name] else {
         throw GraphQLError("Variable \"\(name)\" was not provided.")
       }
+      return value.jsonEncodableValue?.jsonValue
 
-      switch value {
-      case let .variable(nestedName) where name == nestedName:
-        throw GraphQLError("Variable \"\(name)\" is infinitely recursive.")
-      default:
-        return try value.evaluate(with: variables)
-      }
+    case let .scalar(value):
+      return value
 
     case let .list(array):
-      return try evaluate(values: array, with: variables)
+      return try InputValue.evaluate(array, with: variables)
 
     case let .object(dictionary):
-      return try evaluate(values: dictionary, with: variables)
+      return try InputValue.evaluate(dictionary, with: variables)
 
-    case .none:
+    case .null:
       return NSNull()
     }
   }
 
-  private func evaluate(values: [InputValue], with variables: [String: InputValue]?) throws -> [JSONValue] {
-    try values.map { try $0.evaluate(with: variables) }
+  fileprivate static func evaluate(
+    _ values: [InputValue],
+    with variables: GraphQLOperation.Variables?
+  ) throws -> [JSONValue] {
+    try values.compactMap { try $0.evaluate(with: variables) }
   }
 
-  private func evaluate(values: [String: InputValue], with variables: [String: InputValue]?) throws -> JSONObject {
-    var jsonObject = JSONObject(minimumCapacity: values.count)
-    for (key, value) in values {
-      let evaluatedValue = try value.evaluate(with: variables)
-      if !(evaluatedValue is NSNull) {
-        jsonObject[key] = evaluatedValue
-      }
-    }
-    return jsonObject
+  fileprivate static func evaluate(
+    _ values: [String: InputValue],
+    with variables: GraphQLOperation.Variables?
+  ) throws -> JSONObject {
+    try values.compactMapValues { try $0.evaluate(with: variables) }
   }
 }
diff --git a/Sources/Apollo/JSONSerializationFormat.swift b/Sources/Apollo/JSONSerializationFormat.swift
index 156b57556b..077d86b6cd 100644
--- a/Sources/Apollo/JSONSerializationFormat.swift
+++ b/Sources/Apollo/JSONSerializationFormat.swift
@@ -11,6 +11,10 @@ public final class JSONSerializationFormat {
     return try JSONSerialization.sortedData(withJSONObject: value.jsonValue)
   }
 
+  public class func serialize(value: JSONObject) throws -> Data {
+    return try JSONSerialization.sortedData(withJSONObject: value)
+  }
+
   public class func deserialize(data: Data) throws -> JSONValue {
     return try JSONSerialization.jsonObject(with: data, options: [])
   }
diff --git a/Sources/Apollo/RequestBodyCreator.swift b/Sources/Apollo/RequestBodyCreator.swift
index 164a6c73a8..9d1cc66287 100644
--- a/Sources/Apollo/RequestBodyCreator.swift
+++ b/Sources/Apollo/RequestBodyCreator.swift
@@ -13,25 +13,32 @@ public protocol RequestBodyCreator {
   ///   - sendQueryDocument: Whether or not to send the full query document. Should default to `true`.
   ///   - autoPersistQuery: Whether to use auto-persisted query information. Should default to `false`.
   /// - Returns: The created `GraphQLMap`
-  func requestBody<Operation: GraphQLOperation>(for operation: Operation,
-                                                sendOperationIdentifiers: Bool,
-                                                sendQueryDocument: Bool,
-                                                autoPersistQuery: Bool) -> GraphQLMap
+  func requestBody<Operation: GraphQLOperation>(
+    for operation: Operation,
+    sendOperationIdentifiers: Bool,
+    sendQueryDocument: Bool,
+    autoPersistQuery: Bool
+  ) -> JSONEncodableDictionary
 }
 
 // MARK: - Default Implementation
 
 extension RequestBodyCreator {
   
-  public func requestBody<Operation: GraphQLOperation>(for operation: Operation,
-                                                       sendOperationIdentifiers: Bool,
-                                                       sendQueryDocument: Bool,
-                                                       autoPersistQuery: Bool) -> GraphQLMap {
-    var body: GraphQLMap = [
-      "variables": operation.variables?.jsonObject,
+  public func requestBody<Operation: GraphQLOperation>(
+    for operation: Operation,
+    sendOperationIdentifiers: Bool,
+    sendQueryDocument: Bool,
+    autoPersistQuery: Bool
+  ) -> JSONEncodableDictionary {
+    var body: JSONEncodableDictionary = [
       "operationName": operation.operationName,
     ]
 
+    if let variables = operation.variables {
+      body["variables"] = variables.jsonEncodableObject
+    }
+
     if sendOperationIdentifiers {
       guard let operationIdentifier = operation.operationIdentifier else {
         preconditionFailure("To send operation identifiers, Apollo types must be generated with operationIdentifiers")
diff --git a/Sources/Apollo/UploadRequest.swift b/Sources/Apollo/UploadRequest.swift
index d15f3ad0e3..a2767e63a4 100644
--- a/Sources/Apollo/UploadRequest.swift
+++ b/Sources/Apollo/UploadRequest.swift
@@ -75,15 +75,15 @@ open class UploadRequest<Operation: GraphQLOperation>: HTTPRequest<Operation> {
                                                      sendOperationIdentifiers: shouldSendOperationID,
                                                      sendQueryDocument: true,
                                                      autoPersistQuery: false)
-    var variables = fields["variables"] as? GraphQLMap ?? GraphQLMap()
+    var variables = fields["variables"] as? JSONEncodableDictionary ?? JSONEncodableDictionary()
     for fieldName in fieldsForFiles {
       if
         let value = variables[fieldName],
         let arrayValue = value as? [JSONEncodable] {
-        let arrayOfNils: [JSONEncodable?] = arrayValue.map { _ in nil }
+        let arrayOfNils: [JSONEncodable?] = arrayValue.map { _ in NSNull() }
           variables.updateValue(arrayOfNils, forKey: fieldName)
       } else {
-        variables.updateValue(nil, forKey: fieldName)
+        variables.updateValue(NSNull(), forKey: fieldName)
       }
     }
     fields["variables"] = variables
diff --git a/Sources/ApolloAPI/GraphQLEnum.swift b/Sources/ApolloAPI/GraphQLEnum.swift
index 6ef3e7b22e..3e794eb84b 100644
--- a/Sources/ApolloAPI/GraphQLEnum.swift
+++ b/Sources/ApolloAPI/GraphQLEnum.swift
@@ -1,10 +1,18 @@
+/// A protocol that a generated enum from a GraphQL schema conforms to.
+/// This allows it to be wrapped in a `GraphQLEnum` and be used as an input value for operations.
+public protocol EnumType:
+  RawRepresentable,
+  CaseIterable,
+  JSONEncodable,
+  GraphQLOperationVariableValue
+where RawValue == String {}
+
 /// A generic enum that wraps a generated enum from a GraphQL Schema.
 ///
 /// `GraphQLEnum` provides an `__unknown` case that is used when the response returns a value that
 /// is not recognized as a valid enum case. This is usually caused by future cases added to the enum
 /// on the schema after code generation.
-public enum GraphQLEnum<T>: CaseIterable, Equatable, RawRepresentable
-where T: RawRepresentable & CaseIterable, T.RawValue == String {
+public enum GraphQLEnum<T: EnumType>: CaseIterable, Equatable, RawRepresentable {
   public typealias RawValue = String
 
   /// A recognized case of the wrapped enum.
diff --git a/Sources/ApolloAPI/GraphQLNullable.swift b/Sources/ApolloAPI/GraphQLNullable.swift
new file mode 100644
index 0000000000..8cd0b1701b
--- /dev/null
+++ b/Sources/ApolloAPI/GraphQLNullable.swift
@@ -0,0 +1,34 @@
+import Foundation
+
+@dynamicMemberLookup
+public enum GraphQLNullable<Wrapped>: ExpressibleByNilLiteral {
+
+  /// The absence of a value.
+  /// Functionally equivalent to `nil`.
+  case none
+
+  /// The presence of an explicity null value.
+  /// Functionally equivalent to `NSNull`
+  case null
+
+  /// The presence of a value, stored as `Wrapped`
+  case some(Wrapped)
+
+  public var unwrapped: Wrapped? {
+    guard case let .some(wrapped) = self else { return nil }
+    return wrapped
+  }
+
+  public var unsafelyUnwrapped: Wrapped {
+    guard case let .some(wrapped) = self else { fatalError("Force unwrap Nullable value failed!") }
+    return wrapped
+  }
+
+  public subscript<T>(dynamicMember path: KeyPath<Wrapped, T>) -> T? {
+    unwrapped?[keyPath: path]
+  }
+
+  public init(nilLiteral: ()) {
+    self = .none
+  }  
+}
diff --git a/Sources/ApolloAPI/GraphQLOperation.swift b/Sources/ApolloAPI/GraphQLOperation.swift
index 44e6faa3f6..03661b3f8d 100644
--- a/Sources/ApolloAPI/GraphQLOperation.swift
+++ b/Sources/ApolloAPI/GraphQLOperation.swift
@@ -1,3 +1,5 @@
+import Foundation
+
 public enum GraphQLOperationType {
   case query
   case mutation
@@ -5,6 +7,8 @@ public enum GraphQLOperationType {
 }
 
 public protocol GraphQLOperation: AnyObject {
+  typealias Variables = [String: GraphQLOperationVariableValue]
+
   var operationType: GraphQLOperationType { get }
 
   var operationDefinition: String { get }
@@ -13,8 +17,7 @@ public protocol GraphQLOperation: AnyObject {
 
   var queryDocument: String { get }
 
-#warning("TODO: We need to support setting a null value AND a nil value. Considering just going back to using GraphQLMap, or else this should be [String: GraphQLOptional<InputValue>].")
-  var variables: [String: InputValue]? { get }
+  var variables: Variables? { get }
 
   associatedtype Data: RootSelectionSet
 }
@@ -28,7 +31,7 @@ public extension GraphQLOperation {
     return nil
   }
 
-  var variables: [String: InputValue]? {
+  var variables: Variables? {
     return nil
   }
 }
@@ -47,3 +50,32 @@ public protocol GraphQLSubscription: GraphQLOperation {}
 public extension GraphQLSubscription {
   var operationType: GraphQLOperationType { return .subscription }
 }
+
+// MARK: - GraphQLOperationVariableValue
+
+public protocol GraphQLOperationVariableValue {
+  var jsonEncodableValue: JSONEncodable? { get }
+}
+
+extension Array: GraphQLOperationVariableValue where Element: GraphQLOperationVariableValue {}
+
+extension Dictionary: GraphQLOperationVariableValue where Key == String, Value == GraphQLOperationVariableValue {
+  public var jsonEncodableValue: JSONEncodable? { jsonEncodableObject }
+  public var jsonEncodableObject: JSONEncodableDictionary {
+    compactMapValues { $0.jsonEncodableValue }
+  }
+}
+
+extension GraphQLNullable: GraphQLOperationVariableValue where Wrapped: JSONEncodable {
+  public var jsonEncodableValue: JSONEncodable? {
+    switch self {
+    case .none: return nil
+    case .null: return NSNull()
+    case let .some(value): return value
+    }
+  }
+}
+
+extension JSONEncodable where Self: GraphQLOperationVariableValue {
+  public var jsonEncodableValue: JSONEncodable? { self }
+}
diff --git a/Sources/ApolloAPI/GraphQLOptional.swift b/Sources/ApolloAPI/GraphQLOptional.swift
deleted file mode 100644
index 2b783d4f3e..0000000000
--- a/Sources/ApolloAPI/GraphQLOptional.swift
+++ /dev/null
@@ -1,64 +0,0 @@
-import Foundation
-
-public enum GraphQLOptional<T> {
-  case notPresent
-  case nullValue
-  case value(T)
-}
-
-extension GraphQLOptional: Hashable where T: Hashable {
-  
-  public func hash(into hasher: inout Hasher) {
-    switch self {
-    case .notPresent,
-        .nullValue:
-      // no-op
-      break
-    case .value(let hashableType):
-      hashableType.hash(into: &hasher)
-    }
-  }
-}
-
-extension GraphQLOptional: Equatable where T: Equatable {
-  public static func ==(lhs: GraphQLOptional, rhs: GraphQLOptional) -> Bool {
-    switch (lhs, rhs) {
-    case (.notPresent, .notPresent),
-      (.nullValue, .nullValue):
-      return true
-    case (.value(let lhsValue), .value(let rhsValue)):
-      return lhsValue == rhsValue
-    default:
-      return false
-    }
-  }
-}
-
-public extension KeyedEncodingContainer {
-
-  mutating func encodeGraphQLOptional<T: Codable>(_ optional: GraphQLOptional<T>, forKey key: K) throws {
-    switch optional {
-    case .notPresent:
-      break
-    case .nullValue:
-      try self.encodeNil(forKey: key)
-    case .value(let value):
-      try self.encode(value, forKey: key)
-    }
-  }
-}
-
-public extension KeyedDecodingContainer {
-
-  func decodeGraphQLOptional<T: Codable>(forKey key: K) throws -> GraphQLOptional<T> {
-    if self.contains(key) {
-      if let value = try? self.decode(T.self, forKey: key) {
-        return .value(value)
-      } else {
-        return .nullValue
-      }
-    } else {
-      return .notPresent
-    }
-  }
-}
diff --git a/Sources/ApolloAPI/InputValue.swift b/Sources/ApolloAPI/InputValue.swift
index dbb0ea4fa2..9e77ac0bd2 100644
--- a/Sources/ApolloAPI/InputValue.swift
+++ b/Sources/ApolloAPI/InputValue.swift
@@ -1,7 +1,7 @@
 import Foundation
 
 #warning("TODO: It might be more performant to just use the raw values like before commit: e7a9b2c27f9d01764943f1aa7ff9d759d8762bff - We should run performance tests and try reverting and see what performance is like.")
-/// Represents an input value to an argument on a `GraphQLField`'s `FieldArguments`.
+/// Represents an input value to an argument on a `Selection.Field`'s `Arguments`.
 ///
 /// - See: [GraphQLSpec - Input Values](http://spec.graphql.org/June2018/#sec-Input-Values)
 public indirect enum InputValue {
@@ -24,22 +24,10 @@ public indirect enum InputValue {
   case object([String: InputValue])
 
   /// A null input value.
+  ///
+  /// A null input value indicates an intentional inclusion of a value for a field argument as null.
   /// - See: [GraphQLSpec - Input Values - Null Value](http://spec.graphql.org/June2018/#sec-Null-Value)
-  case none
-}
-
-// MARK: - JSONEncodable
-
-extension InputValue: JSONEncodable {
-  public var jsonValue: JSONValue {
-    switch self {
-    case let .scalar(value): return value
-    case let .variable(variableName): return "$\(variableName)"
-    case let .list(values): return values.map { $0.jsonValue }
-    case let .object(valueObject): return valueObject.mapValues { $0.jsonValue }
-    case .none: return NSNull()
-    }
-  }
+  case null
 }
 
 // MARK: - InputValueConvertible
@@ -68,21 +56,7 @@ extension InputValueConvertible where Self: RawRepresentable, RawValue == String
   @inlinable public var asInputValue: InputValue { .scalar(rawValue) }
 }
 
-extension Optional: InputValueConvertible where Wrapped: InputValueConvertible {
-  @inlinable public var asInputValue: InputValue {
-    switch self {
-    case .none: return .none
-    case let .some(value): return value.asInputValue
-    }
-  }
-}
-
 // MARK: - Expressible as literals
-extension InputValue: ExpressibleByNilLiteral {
-  @inlinable public init(nilLiteral: ()) {
-    self = .none
-  }
-}
 
 extension InputValue: ExpressibleByStringLiteral {
   @inlinable public init(stringLiteral value: StringLiteralType) {
@@ -121,14 +95,6 @@ extension InputValue: ExpressibleByDictionaryLiteral {
   }
 }
 
-// MARK = Variable Dictionary Conversion
-
-extension Dictionary where Key == String, Value == InputValueConvertible {
-  @inlinable public func toInputVariables() -> [String: InputValue] {
-    mapValues { $0.asInputValue }
-  }
-}
-
 // MARK: Equatable Conformance
 
 extension InputValue: Equatable {
@@ -149,7 +115,7 @@ extension InputValue: Equatable {
       return lhsValue.elementsEqual(rhsValue)
     case let (.object(lhsValue), .object(rhsValue)):
       return lhsValue.elementsEqual(rhsValue, by: { $0.key == $1.key && $0.value == $1.value })
-    case (.none, .none):
+    case (.null, .null):
       return true
     default: return false
     }
diff --git a/Sources/ApolloAPI/JSON.swift b/Sources/ApolloAPI/JSON.swift
index a01fc064f8..16e7364894 100644
--- a/Sources/ApolloAPI/JSON.swift
+++ b/Sources/ApolloAPI/JSON.swift
@@ -2,6 +2,7 @@ import Foundation
 
 public typealias JSONValue = Any
 public typealias JSONObject = [String: JSONValue]
+public typealias JSONEncodableDictionary = [String: JSONEncodable]
 
 public protocol JSONDecodable {
   init(jsonValue value: JSONValue) throws
diff --git a/Sources/ApolloAPI/JSONStandardTypeConversions.swift b/Sources/ApolloAPI/JSONStandardTypeConversions.swift
index 2ead5a9a63..ad1db2380f 100644
--- a/Sources/ApolloAPI/JSONStandardTypeConversions.swift
+++ b/Sources/ApolloAPI/JSONStandardTypeConversions.swift
@@ -69,6 +69,11 @@ extension Bool: JSONDecodable, JSONEncodable {
   }
 }
 
+extension EnumType {
+  public var jsonValue: JSONValue { rawValue }
+}
+
+#warning("might be able to remove these since we are using EnumType")
 extension RawRepresentable where RawValue: JSONDecodable {
   public init(jsonValue value: JSONValue) throws {
     let rawValue = try RawValue(jsonValue: value)
@@ -119,21 +124,13 @@ extension NSNull: JSONEncodable {
   public var jsonValue: JSONValue { self }
 }
 
-extension Dictionary: JSONEncodable {
+extension JSONEncodableDictionary: JSONEncodable {
   public var jsonValue: JSONValue {
     return jsonObject
   }
 
   public var jsonObject: JSONObject {
-    var jsonObject = JSONObject(minimumCapacity: count)
-    for (key, value) in self {
-      if case let (key as String, value as JSONEncodable) = (key, value) {
-        jsonObject[key] = value.jsonValue
-      } else {
-        fatalError("Dictionary is only JSONEncodable if Value is (and if Key is String)")
-      }
-    }
-    return jsonObject
+    mapValues(\.jsonValue)
   }
 }
 
diff --git a/Sources/ApolloAPI/ScalarTypes.swift b/Sources/ApolloAPI/ScalarTypes.swift
index 8a36a09cdb..90b9441a83 100644
--- a/Sources/ApolloAPI/ScalarTypes.swift
+++ b/Sources/ApolloAPI/ScalarTypes.swift
@@ -5,7 +5,8 @@ public protocol ScalarType:
   JSONDecodable,
   JSONEncodable,
   Cacheable,
-  InputValueConvertible {}
+  InputValueConvertible,
+  GraphQLOperationVariableValue {}
 
 extension String: ScalarType {}
 extension Int: ScalarType {}
diff --git a/Sources/ApolloAPI/Selection.swift b/Sources/ApolloAPI/Selection.swift
index ed264ffd20..ed1b9e9a2b 100644
--- a/Sources/ApolloAPI/Selection.swift
+++ b/Sources/ApolloAPI/Selection.swift
@@ -9,8 +9,7 @@ public enum Selection {
   public struct Field {
     public let name: String
     public let alias: String?
-    #warning("TODO: can we just change this to [String: InputValue] and kill Arguments?")
-    public let arguments: Arguments?
+    public let arguments: [String: InputValue]?
     public let type: OutputType
 
     public var responseKey: String {
@@ -21,7 +20,7 @@ public enum Selection {
       _ name: String,
       alias: String? = nil,
       type: OutputType,
-      arguments: Arguments? = nil
+      arguments: [String: InputValue]? = nil
     ) {
       self.name = name
       self.alias = alias
@@ -31,14 +30,6 @@ public enum Selection {
       self.type = type
     }
 
-    public struct Arguments: ExpressibleByDictionaryLiteral {
-      public let arguments: InputValue
-
-      @inlinable public init(dictionaryLiteral elements: (String, InputValue)...) {
-        arguments = .object(Dictionary(elements, uniquingKeysWith: { (_, last) in last }))
-      }
-    }
-
     public indirect enum OutputType {
       case scalar(ScalarType.Type)
       case customScalar(CustomScalarType.Type)
@@ -82,7 +73,7 @@ public enum Selection {
     _ name: String,
     alias: String? = nil,
     _ type: OutputTypeConvertible.Type,
-    arguments: Field.Arguments? = nil
+    arguments: [String: InputValue]? = nil
   ) -> Selection {
     .field(.init(name, alias: alias, type: type.asOutputType, arguments: arguments))
   }  
diff --git a/Sources/ApolloTestSupport/MockOperation.swift b/Sources/ApolloTestSupport/MockOperation.swift
index d473eba0ea..791400c475 100644
--- a/Sources/ApolloTestSupport/MockOperation.swift
+++ b/Sources/ApolloTestSupport/MockOperation.swift
@@ -12,7 +12,7 @@ open class MockOperation<SelectionSet: RootSelectionSet>: GraphQLOperation {
   public var stubbedQueryDocument: String?
   public final var queryDocument: String { stubbedQueryDocument ?? operationDefinition }
 
-  open var variables: [String: InputValue]?
+  open var variables: Variables?
 
   public init(type: GraphQLOperationType = .query) {
     self.operationType = type
diff --git a/Sources/ApolloWebSocket/OperationMessage.swift b/Sources/ApolloWebSocket/OperationMessage.swift
index d0719262b8..2ade22bc8e 100644
--- a/Sources/ApolloWebSocket/OperationMessage.swift
+++ b/Sources/ApolloWebSocket/OperationMessage.swift
@@ -1,5 +1,6 @@
 #if !COCOAPODS
 import Apollo
+import ApolloAPI
 #endif
 import Foundation
 
@@ -20,7 +21,7 @@ final class OperationMessage {
   }
 
   let serializationFormat = JSONSerializationFormat.self
-  let message: GraphQLMap
+  let message: JSONEncodableDictionary
   var serialized: String?
 
   var rawMessage : String? {
@@ -32,10 +33,10 @@ final class OperationMessage {
     }
   }
 
-  init(payload: GraphQLMap? = nil,
+  init(payload: JSONEncodableDictionary? = nil,
        id: String? = nil,
        type: Types = .start) {
-    var message: GraphQLMap = [:]
+    var message: JSONEncodableDictionary = [:]
     if let payload = payload {
       message["payload"] = payload
     }
diff --git a/Sources/ApolloWebSocket/WebSocketTransport.swift b/Sources/ApolloWebSocket/WebSocketTransport.swift
index 145d2db797..2fdd384766 100644
--- a/Sources/ApolloWebSocket/WebSocketTransport.swift
+++ b/Sources/ApolloWebSocket/WebSocketTransport.swift
@@ -97,7 +97,7 @@ public class WebSocketTransport {
     ///  Defaults to true.
     public let connectOnInit: Bool
     /// [optional]The payload to send on connection. Defaults to an empty `GraphQLMap`.
-    public fileprivate(set) var connectingPayload: GraphQLMap?
+    public fileprivate(set) var connectingPayload: JSONEncodableDictionary?
     /// The `RequestBodyCreator` to use when serializing requests. Defaults to an `ApolloRequestBodyCreator`.
     public let requestBodyCreator: RequestBodyCreator
     /// The `OperationMessageIdCreator` used to generate a unique message identifier per request.
@@ -113,7 +113,7 @@ public class WebSocketTransport {
       reconnectionInterval: TimeInterval = 0.5,
       allowSendingDuplicates: Bool = true,
       connectOnInit: Bool = true,
-      connectingPayload: GraphQLMap? = [:],
+      connectingPayload: JSONEncodableDictionary? = [:],
       requestBodyCreator: RequestBodyCreator = ApolloRequestBodyCreator(),
       operationMessageIdCreator: OperationMessageIdCreator = ApolloSequencedOperationMessageIdCreator()
     ) {
@@ -341,7 +341,7 @@ public class WebSocketTransport {
     }
   }
 
-  public func updateConnectingPayload(_ payload: GraphQLMap, reconnectIfConnected: Bool = true) {
+  public func updateConnectingPayload(_ payload: JSONEncodableDictionary, reconnectIfConnected: Bool = true) {
     self.config.connectingPayload = payload
 
     if reconnectIfConnected && isConnected() {
diff --git a/Sources/UploadAPI/API.swift b/Sources/UploadAPI/API.swift
index 4b133e5ea8..105031ad22 100644
--- a/Sources/UploadAPI/API.swift
+++ b/Sources/UploadAPI/API.swift
@@ -60,8 +60,8 @@ public final class UploadMultipleFilesToTheSameParameterMutation: GraphQLMutatio
     self.files = files
   }
 
-  public var variables: [String: InputValue]? {
-    ["files": files].toInputVariables()
+  public var variables: Variables? {
+    ["files": files]
   }
 
   public struct Data: SelectionSet {
@@ -126,8 +126,8 @@ public final class UploadMultipleFilesToDifferentParametersMutation: GraphQLMuta
     self.multipleFiles = multipleFiles
   }
 
-  public var variables: [String: InputValue]? {
-    ["singleFile": singleFile, "multipleFiles": multipleFiles].toInputVariables()
+  public var variables: Variables? {
+    ["singleFile": singleFile, "multipleFiles": multipleFiles]
   }
 
   public struct Data: SelectionSet {
@@ -200,8 +200,8 @@ public final class UploadOneFileMutation: GraphQLMutation {
     self.file = file
   }
 
-  public var variables: [String: InputValue]? {
-    ["file": file].toInputVariables()
+  public var variables: Variables? {
+    ["file": file]
   }
 
   public struct Data: SelectionSet {
diff --git a/Tests/ApolloTests/AutomaticPersistedQueriesTests.swift b/Tests/ApolloTests/AutomaticPersistedQueriesTests.swift
index b2f1fb5839..746dd40f64 100644
--- a/Tests/ApolloTests/AutomaticPersistedQueriesTests.swift
+++ b/Tests/ApolloTests/AutomaticPersistedQueriesTests.swift
@@ -1,4 +1,5 @@
 import XCTest
+import Nimble
 @testable import Apollo
 import ApolloAPI
 import ApolloTestSupport
@@ -25,23 +26,23 @@ class AutomaticPersistedQueriesTests: XCTestCase {
     }
   }
 
-  fileprivate enum MockEnum: String, CaseIterable, InputValueConvertible {
+  fileprivate enum MockEnum: String, EnumType {
     case NEWHOPE
     case JEDI
     case EMPIRE
   }
 
   fileprivate class MockHeroNameQuery: MockQuery<HeroNameSelectionSet> {
-    var episode: MockEnum? {
+    var episode: GraphQLNullable<MockEnum> {
       didSet {
-        self.variables = ["episode": episode].toInputVariables()
+        self.variables = ["episode": episode]
       }
     }
 
-    init(episode: MockEnum? = nil) {
+    init(episode: GraphQLNullable<MockEnum> = .none) {
       self.episode = episode
       super.init()
-      self.variables = ["episode": episode].toInputVariables()
+      self.variables = ["episode": episode]
       self.operationIdentifier = "f6e76545cd03aa21368d9969cb39447f6e836a16717823281803778e7805d671"
       self.operationDefinition = "MockHeroNameQuery - Operation Definition"
     }
@@ -84,7 +85,7 @@ class AutomaticPersistedQueriesTests: XCTestCase {
     if let query = operation as? MockHeroNameQuery{
       if let variables = jsonBody["variables"] as? JSONObject {
         XCTAssertEqual(variables["episode"] as? String,
-                       query.episode?.rawValue,
+                       query.episode.rawValue,
                        file: file,
                        line: line)
       } else {
@@ -156,16 +157,17 @@ class AutomaticPersistedQueriesTests: XCTestCase {
     }
     
     if let variables = url.queryItemDictionary?["variables"] {
-      if let episode = query.episode {
-        XCTAssertEqual(variables,
-                       "{\"episode\":\"\(episode.rawValue)\"}",
-                       file: file,
-                       line: line)
-      } else {
-        XCTAssertEqual(variables,
-                       "{\"episode\":null}",
-                       file: file,
-                       line: line)
+      let expectation = expect(file: file, line: line, variables)
+      switch query.episode {
+      case let .some(episode):
+        expectation.to(equal("{\"episode\":\"\(episode.rawValue)\"}"))
+
+      case .none:
+        #warning("TODO: write test to test this case actually happens")
+        expectation.to(equal("{}"))
+
+      case .null:
+        expectation.to(equal("{\"episode\":null}"))
       }
     } else {
       XCTFail("variables should not be nil",
@@ -252,7 +254,7 @@ class AutomaticPersistedQueriesTests: XCTestCase {
                                                endpointURL: Self.endpoint)
     
     let expectation = self.expectation(description: "Query sent")
-    let query = MockHeroNameQuery(episode: .JEDI)
+    let query = MockHeroNameQuery(episode: .some(.JEDI))
     var lastRequest: URLRequest?
     let _ = network.send(operation: query) { _ in
       lastRequest = mockClient.lastRequest.value
@@ -279,7 +281,7 @@ class AutomaticPersistedQueriesTests: XCTestCase {
                                                autoPersistQueries: true)
     
     let expectation = self.expectation(description: "Query sent")
-    let query = MockHeroNameQuery(episode: .EMPIRE)
+    let query = MockHeroNameQuery(episode: .some(.EMPIRE))
     var lastRequest: URLRequest?
     let _ = network.send(operation: query) { _ in
       lastRequest = mockClient.lastRequest.value
@@ -360,7 +362,7 @@ class AutomaticPersistedQueriesTests: XCTestCase {
                                                useGETForPersistedQueryRetry: true)
     
     let expectation = self.expectation(description: "Query sent")
-    let query = MockHeroNameQuery(episode: .EMPIRE)
+    let query = MockHeroNameQuery(episode: .some(.EMPIRE))
     var lastRequest: URLRequest?
     let _ = network.send(operation: query) { _ in
       lastRequest = mockClient.lastRequest.value
@@ -442,7 +444,7 @@ class AutomaticPersistedQueriesTests: XCTestCase {
                                                autoPersistQueries: true)
     
     let expectation = self.expectation(description: "Query sent")
-    let query = MockHeroNameQuery(episode: .EMPIRE)
+    let query = MockHeroNameQuery(episode: .some(.EMPIRE))
     var lastRequest: URLRequest?
     let _ = network.send(operation: query) { _ in
       lastRequest = mockClient.lastRequest.value
@@ -470,7 +472,7 @@ class AutomaticPersistedQueriesTests: XCTestCase {
                                                useGETForQueries: true)
     
     let expectation = self.expectation(description: "Query sent")
-    let query = MockHeroNameQuery(episode: .EMPIRE)
+    let query = MockHeroNameQuery(episode: .some(.EMPIRE))
     var lastRequest: URLRequest?
     let _ = network.send(operation: query) { _ in
       lastRequest = mockClient.lastRequest.value
@@ -498,7 +500,7 @@ class AutomaticPersistedQueriesTests: XCTestCase {
                                                useGETForPersistedQueryRetry: true)
     
     let expectation = self.expectation(description: "Query sent")
-    let query = MockHeroNameQuery(episode: .EMPIRE)
+    let query = MockHeroNameQuery(episode: .some(.EMPIRE))
     var lastRequest: URLRequest?
     let _ = network.send(operation: query) { _ in
       lastRequest = mockClient.lastRequest.value
diff --git a/Tests/ApolloTests/Cache/WatchQueryTests.swift b/Tests/ApolloTests/Cache/WatchQueryTests.swift
index ed55ad73de..ae692a186e 100644
--- a/Tests/ApolloTests/Cache/WatchQueryTests.swift
+++ b/Tests/ApolloTests/Cache/WatchQueryTests.swift
@@ -1,4 +1,5 @@
 import XCTest
+import Nimble
 @testable import Apollo
 import ApolloAPI
 import ApolloTestSupport
@@ -263,7 +264,7 @@ class WatchQueryTests: XCTestCase, CacheDependentTesting {
     runActivity("Fetch same query from server with different argument") { _ in
       let serverRequestExpectation =
         server.expect(MockQuery<GivenMockSelectionSet>.self) { request in
-          XCTAssertEqual(request.operation.variables?["episode"], .scalar("JEDI"))
+          expect(request.operation.variables?["episode"] as? String).to(equal("JEDI"))
 
           return [
             "data": [
@@ -323,7 +324,7 @@ class WatchQueryTests: XCTestCase, CacheDependentTesting {
     
     runActivity("Initial fetch from server") { _ in
       let serverRequestExpectation = server.expect(MockQuery<GivenSelectionSet>.self) { request in
-        XCTAssertEqual(request.operation.variables?["episode"], "EMPIRE")
+        expect(request.operation.variables?["episode"] as? String).to(equal("EMPIRE"))
         return [
           "data": [
             "hero": [
@@ -353,7 +354,7 @@ class WatchQueryTests: XCTestCase, CacheDependentTesting {
     
     runActivity("Fetch same query from server with different argument but returning same object with changed data") { _ in
       let serverRequestExpectation = server.expect(MockQuery<GivenSelectionSet>.self) { request in
-        XCTAssertEqual(request.operation.variables?["episode"], "JEDI")
+        expect(request.operation.variables?["episode"] as? String).to(equal("JEDI"))        
         return [
           "data": [
             "hero": [
diff --git a/Tests/ApolloTests/CacheKeyForFieldTests.swift b/Tests/ApolloTests/CacheKeyForFieldTests.swift
index b16d3de760..ecb62f6d1b 100644
--- a/Tests/ApolloTests/CacheKeyForFieldTests.swift
+++ b/Tests/ApolloTests/CacheKeyForFieldTests.swift
@@ -41,8 +41,20 @@ class CacheKeyForFieldTests: XCTestCase {
     XCTAssertEqual(field.test_cacheKey, "hero(episode:1.99)")
   }
 
-  func testFieldWithNilArgument() {
-    let field = Selection.Field("hero", type: .scalar(String.self), arguments: ["episode": nil])
+  func testFieldWithNullArgument() {
+    let field = Selection.Field("hero", type: .scalar(String.self), arguments: ["episode": .null])
+    XCTAssertEqual(field.test_cacheKey, "hero(episode:null)")
+  }
+
+  func testFieldWithNestedNullArgument() throws {
+    let field = Selection.Field("hero",
+                                type: .scalar(String.self),
+                                arguments: ["nested": ["foo": 1, "bar": InputValue.null]])
+    XCTAssertEqual(field.test_cacheKey, "hero([nested:bar:null,foo:1])")
+  }
+
+  func testFieldWithArgumentOmitted() {
+    let field = Selection.Field("hero", type: .scalar(String.self), arguments: [:])
     XCTAssertEqual(field.test_cacheKey, "hero")
   }
 
@@ -58,7 +70,7 @@ class CacheKeyForFieldTests: XCTestCase {
   
   func testFieldWithDictionaryArgumentWithVariables() throws {
     let field = Selection.Field("hero", type: .scalar(String.self), arguments: ["nested": ["foo": InputValue.variable("a"), "bar": InputValue.variable("b")]])
-    let variables: [String: InputValue] = ["a": 1, "b": 2]
+    let variables = ["a": 1, "b": 2]
     XCTAssertEqual(try field.cacheKey(with: variables), "hero([nested:bar:2,foo:1])")
   }
   
@@ -76,13 +88,25 @@ class CacheKeyForFieldTests: XCTestCase {
   
   func testFieldWithVariableArgument() throws {
     let field = Selection.Field("hero", type: .scalar(String.self), arguments: ["episode": .variable("episode")])
-    let variables: [String: InputValue] = ["episode": "JEDI"]
+    let variables = ["episode": "JEDI"]
     XCTAssertEqual(try field.cacheKey(with: variables), "hero(episode:JEDI)")
   }
   
   func testFieldWithVariableArgumentWithNil() throws {
     let field = Selection.Field("hero", type: .scalar(String.self), arguments: ["episode": .variable("episode")])
-    let variables: [String: InputValue] = ["episode": nil]
+    let variables: GraphQLOperation.Variables = ["episode": GraphQLNullable<String>.none]
     XCTAssertEqual(try field.cacheKey(with: variables), "hero")
   }
+
+  func testFieldWithVariableArgumentWithNull() throws {
+    let field = Selection.Field("hero", type: .scalar(String.self), arguments: ["episode": .variable("episode")])
+    let variables = ["episode": GraphQLNullable<String>.null]
+    XCTAssertEqual(try field.cacheKey(with: variables), "hero(episode:null)")
+  }
+
+  func testFieldWithVariableArgumentWithNestedNull() throws {
+    let field = Selection.Field("hero", type: .scalar(String.self), arguments: ["nested": ["foo": InputValue.variable("a"), "bar": InputValue.variable("b")]])
+    let variables: GraphQLOperation.Variables = ["a": 1, "b": GraphQLNullable<String>.null]
+    XCTAssertEqual(try field.cacheKey(with: variables), "hero([nested:bar:null,foo:1])")
+  }
 }
diff --git a/Tests/ApolloTests/GETTransformerTests.swift b/Tests/ApolloTests/GETTransformerTests.swift
index ff56ece31b..be5adc62f0 100644
--- a/Tests/ApolloTests/GETTransformerTests.swift
+++ b/Tests/ApolloTests/GETTransformerTests.swift
@@ -20,7 +20,7 @@ class GETTransformerTests: XCTestCase {
     super.tearDown()
   }
 
-  private enum MockEnum: String, CaseIterable, InputValueConvertible {
+  private enum MockEnum: String, EnumType {
     case LARGE
     case AVERAGE
     case SMALL
@@ -64,7 +64,7 @@ query MockQuery($param: MockEnum) {
   }
 }
 """
-    operation.variables = ["param": MockEnum.LARGE.asInputValue]
+    operation.variables = ["param": MockEnum.LARGE]
 
     let body = requestBodyCreator.requestBody(for: operation,
                                               sendOperationIdentifiers: false,
@@ -113,18 +113,17 @@ query MockQuery($a: String, $b: Boolean!) {
     operation.stubbedQueryDocument = "query MockQuery {}"
     operation.operationIdentifier = "4d465fbc6e3731d01102504850"
     
-    let persistedQuery: GraphQLMap = [
+    let persistedQuery: JSONEncodableDictionary = [
       "version": 1,
-      "sha256Hash": operation.operationIdentifier
+      "sha256Hash": operation.operationIdentifier!
     ]
     
-    let extensions: GraphQLMap = [
+    let extensions: JSONEncodableDictionary = [
       "persistedQuery": persistedQuery
     ]
     
-    let body: GraphQLMap = [
+    let body: JSONEncodableDictionary = [
       "query": operation.queryDocument,
-      "variables": operation.variables,
       "extensions": extensions
     ]
     
@@ -140,13 +139,12 @@ query MockQuery($a: String, $b: Boolean!) {
   func test__createGetURL__queryWithParameter_withPlusSign_encodesPlusSign() throws {
     let operation = MockOperation.mock()
 
-    let extensions: GraphQLMap = [
+    let extensions: JSONEncodableDictionary = [
       "testParam": "+Test+Test"
     ]
 
-    let body: GraphQLMap = [
+    let body: JSONEncodableDictionary = [
       "query": operation.queryDocument,
-      "variables": operation.variables,
       "extensions": extensions
     ]
 
@@ -162,13 +160,12 @@ query MockQuery($a: String, $b: Boolean!) {
   func test__createGetURL__queryWithParameter_withAmpersand_encodesAmpersand() throws {
     let operation = MockOperation.mock()
 
-    let extensions: GraphQLMap = [
+    let extensions: JSONEncodableDictionary = [
       "testParam": "Test&Test"
     ]
 
-    let body: GraphQLMap = [
+    let body: JSONEncodableDictionary = [
       "query": operation.queryDocument,
-      "variables": operation.variables,
       "extensions": extensions
     ]
 
@@ -185,17 +182,16 @@ query MockQuery($a: String, $b: Boolean!) {
     operation.operationName = "TestOpName"
     operation.operationIdentifier = "4d465fbc6e3731d01102504850"
     
-    let persistedQuery: GraphQLMap = [
+    let persistedQuery: JSONEncodableDictionary = [
       "version": 1,
-      "sha256Hash": operation.operationIdentifier
+      "sha256Hash": operation.operationIdentifier!
     ]
     
-    let extensions: GraphQLMap = [
+    let extensions: JSONEncodableDictionary = [
       "persistedQuery": persistedQuery
     ]
     
-    let body: GraphQLMap = [
-      "variables": operation.variables,
+    let body: JSONEncodableDictionary = [
       "extensions": extensions
     ]
     
@@ -219,7 +215,7 @@ query MockQuery($param: String) {
   }
 }
 """
-    operation.variables = ["param": .none]
+    operation.variables = ["param": GraphQLNullable<String>.null]
 
     let body = requestBodyCreator.requestBody(for: operation,
                                               sendOperationIdentifiers: false,
@@ -238,13 +234,12 @@ query MockQuery($param: String) {
   func test__createGetURL__urlHasExistingParameters_encodesURLIncludingExistingParameters_atStartOfQueryParameters() throws {
     let operation = MockOperation.mock()
 
-    let extensions: GraphQLMap = [
+    let extensions: JSONEncodableDictionary = [
       "testParam": "Test&Test"
     ]
 
-    let body: GraphQLMap = [
+    let body: JSONEncodableDictionary = [
       "query": operation.queryDocument,
-      "variables": operation.variables,
       "extensions": extensions
     ]
 
@@ -260,7 +255,7 @@ query MockQuery($param: String) {
   }
 
 	func test__createGetURL__withEmptyQueryParameter_returnsURL() throws {
-		let body: GraphQLMap = [:]
+		let body: JSONEncodableDictionary = [:]
 		let transformer = GraphQLGETTransformer(body: body, url: Self.url)
 		let url = transformer.createGetURL()
 
diff --git a/Tests/ApolloTests/GraphQLExecutor_ResultNormalizer_FromResponse_Tests.swift b/Tests/ApolloTests/GraphQLExecutor_ResultNormalizer_FromResponse_Tests.swift
index 403e4fb8ad..39d29c2722 100644
--- a/Tests/ApolloTests/GraphQLExecutor_ResultNormalizer_FromResponse_Tests.swift
+++ b/Tests/ApolloTests/GraphQLExecutor_ResultNormalizer_FromResponse_Tests.swift
@@ -19,7 +19,7 @@ class GraphQLExecutor_ResultNormalizer_FromResponse_Tests: XCTestCase {
 
   private func normalizeRecords(
     _ selectionSet: RootSelectionSet.Type,
-    with variables: [String: InputValue]? = nil,
+    with variables: GraphQLOperation.Variables? = nil,
     from object: JSONObject
   ) throws -> RecordSet {
     return try GraphQLExecutor_ResultNormalizer_FromResponse_Tests.executor.execute(
@@ -76,7 +76,7 @@ class GraphQLExecutor_ResultNormalizer_FromResponse_Tests: XCTestCase {
       }
     }
     
-    let variables: [String: InputValue] = ["episode": "JEDI"]
+    let variables = ["episode": "JEDI"]
 
     let object: JSONObject = [
       "hero": ["__typename": "Droid", "name": "R2-D2"]
@@ -95,7 +95,7 @@ class GraphQLExecutor_ResultNormalizer_FromResponse_Tests: XCTestCase {
 
   func test__execute__givenObjectWithNoCacheKey_forFieldWithEnumArgument_normalizesRecordToPathFromQueryRootIncludingArgument() throws {
     // given
-    enum MockEnum: String, CaseIterable, InputValueConvertible {
+    enum MockEnum: String, EnumType {
       case NEWHOPE
       case EMPIRE
       case JEDI
@@ -113,7 +113,7 @@ class GraphQLExecutor_ResultNormalizer_FromResponse_Tests: XCTestCase {
       }
     }
 
-    let variables: [String: InputValue] = ["episode": MockEnum.EMPIRE].toInputVariables()
+    let variables = ["episode": MockEnum.EMPIRE]
 
     let object: JSONObject = [
       "hero": ["__typename": "Droid", "name": "R2-D2"]
diff --git a/Tests/ApolloTests/GraphQLExecutor_SelectionSetMapper_FromResponse_Tests.swift b/Tests/ApolloTests/GraphQLExecutor_SelectionSetMapper_FromResponse_Tests.swift
index 444f2303bc..1bfbe799d3 100644
--- a/Tests/ApolloTests/GraphQLExecutor_SelectionSetMapper_FromResponse_Tests.swift
+++ b/Tests/ApolloTests/GraphQLExecutor_SelectionSetMapper_FromResponse_Tests.swift
@@ -20,7 +20,7 @@ class GraphQLExecutor_SelectionSetMapper_FromResponse_Tests: XCTestCase {
   private func readValues<T: RootSelectionSet>(
     _ selectionSet: T.Type,
     from object: JSONObject,
-    variables: [String: InputValue]? = nil
+    variables: GraphQLOperation.Variables? = nil
   ) throws -> T {
     return try GraphQLExecutor_SelectionSetMapper_FromResponse_Tests.executor.execute(
       selectionSet: selectionSet,
@@ -205,7 +205,7 @@ class GraphQLExecutor_SelectionSetMapper_FromResponse_Tests: XCTestCase {
 
   // MARK: Nonnull Enum Value
 
-  private enum MockEnum: String, CaseIterable, InputValueConvertible {
+  private enum MockEnum: String, EnumType {
     case SMALL
     case MEDIUM
     case LARGE
@@ -814,7 +814,7 @@ class GraphQLExecutor_SelectionSetMapper_FromResponse_Tests: XCTestCase {
       ]}
     }
     let object: JSONObject = ["name": "Luke Skywalker"]
-    let variables = ["variable": true].toInputVariables()
+    let variables = ["variable": true]
 
     // when
     let data = try readValues(GivenSelectionSet.self, from: object, variables: variables)
@@ -831,7 +831,7 @@ class GraphQLExecutor_SelectionSetMapper_FromResponse_Tests: XCTestCase {
       ]}
     }
     let object: JSONObject = ["name": "Luke Skywalker"]
-    let variables = ["variable": false].toInputVariables()
+    let variables = ["variable": false]
 
     // when
     let data = try readValues(GivenSelectionSet.self, from: object, variables: variables)
@@ -849,7 +849,7 @@ class GraphQLExecutor_SelectionSetMapper_FromResponse_Tests: XCTestCase {
       ]}
     }
     let object: JSONObject = ["name": "Luke Skywalker", "id": "1234"]
-    let variables = ["variable": false].toInputVariables()
+    let variables = ["variable": false]
 
     // when
     let data = try readValues(GivenSelectionSet.self, from: object, variables: variables)
@@ -870,7 +870,7 @@ class GraphQLExecutor_SelectionSetMapper_FromResponse_Tests: XCTestCase {
       ]}
     }
     let object: JSONObject = ["name": "Luke Skywalker", "id": "1234"]
-    let variables = ["variable": true].toInputVariables()
+    let variables = ["variable": true]
 
     // when
     let data = try readValues(GivenSelectionSet.self, from: object, variables: variables)
@@ -891,7 +891,7 @@ class GraphQLExecutor_SelectionSetMapper_FromResponse_Tests: XCTestCase {
       ]}
     }
     let object: JSONObject = ["name": "Luke Skywalker", "id": "1234"]
-    let variables = ["variable": false].toInputVariables()
+    let variables = ["variable": false]
 
     // when
     let data = try readValues(GivenSelectionSet.self, from: object, variables: variables)
@@ -916,7 +916,7 @@ class GraphQLExecutor_SelectionSetMapper_FromResponse_Tests: XCTestCase {
       ]}
     }
     let object: JSONObject = ["name": "Luke Skywalker", "id": "1234"]
-    let variables = ["variable": true].toInputVariables()
+    let variables = ["variable": true]
 
     // when
     let data = try readValues(GivenSelectionSet.self, from: object, variables: variables)
@@ -941,7 +941,7 @@ class GraphQLExecutor_SelectionSetMapper_FromResponse_Tests: XCTestCase {
       ]}
     }
     let object: JSONObject = ["name": "Luke Skywalker", "id": "1234"]
-    let variables = ["variable": false].toInputVariables()
+    let variables = ["variable": false]
 
     // when
     let data = try readValues(GivenSelectionSet.self, from: object, variables: variables)
@@ -972,7 +972,7 @@ class GraphQLExecutor_SelectionSetMapper_FromResponse_Tests: XCTestCase {
     let object: JSONObject = ["__typename": "Person",
                               "name": "Luke Skywalker",
                               "id": "1234"]
-    let variables = ["variable": true].toInputVariables()
+    let variables = ["variable": true]
 
     // when
     let data = try readValues(GivenSelectionSet.self, from: object, variables: variables)
@@ -1003,7 +1003,7 @@ class GraphQLExecutor_SelectionSetMapper_FromResponse_Tests: XCTestCase {
     let object: JSONObject = ["__typename": "Person",
                               "name": "Luke Skywalker",
                               "id": "1234"]
-    let variables = ["variable": false].toInputVariables()
+    let variables = ["variable": false]
 
     // when
     let data = try readValues(GivenSelectionSet.self, from: object, variables: variables)
@@ -1034,7 +1034,7 @@ class GraphQLExecutor_SelectionSetMapper_FromResponse_Tests: XCTestCase {
     let object: JSONObject = ["__typename": "Person",
                               "name": "Luke Skywalker",
                               "id": "1234"]
-    let variables = ["variable": true].toInputVariables()
+    let variables = ["variable": true]
 
     // when
     let data = try readValues(GivenSelectionSet.self, from: object, variables: variables)
@@ -1065,7 +1065,7 @@ class GraphQLExecutor_SelectionSetMapper_FromResponse_Tests: XCTestCase {
     let object: JSONObject = ["__typename": "Person",
                               "name": "Luke Skywalker",
                               "id": "1234"]
-    let variables = ["variable": true].toInputVariables()
+    let variables = ["variable": true]
 
     // when
     let data = try readValues(GivenSelectionSet.self, from: object, variables: variables)
@@ -1096,7 +1096,7 @@ class GraphQLExecutor_SelectionSetMapper_FromResponse_Tests: XCTestCase {
     let object: JSONObject = ["__typename": "Person",
                               "name": "Luke Skywalker",
                               "id": "1234"]
-    let variables = ["variable": false].toInputVariables()
+    let variables = ["variable": false]
 
     // when
     let data = try readValues(GivenSelectionSet.self, from: object, variables: variables)
@@ -1132,7 +1132,7 @@ class GraphQLExecutor_SelectionSetMapper_FromResponse_Tests: XCTestCase {
     let object: JSONObject = ["__typename": "Person",
                               "name": "Luke Skywalker",
                               "id": "1234"]
-    let variables = ["variable": true].toInputVariables()
+    let variables = ["variable": true]
 
     // when
     let data = try readValues(GivenSelectionSet.self, from: object, variables: variables)
@@ -1151,7 +1151,7 @@ class GraphQLExecutor_SelectionSetMapper_FromResponse_Tests: XCTestCase {
       ]}
     }
     let object: JSONObject = ["name": "Luke Skywalker"]
-    let variables = ["variable": false].toInputVariables()
+    let variables = ["variable": false]
 
     // when
     let data = try readValues(GivenSelectionSet.self, from: object, variables: variables)
@@ -1168,7 +1168,7 @@ class GraphQLExecutor_SelectionSetMapper_FromResponse_Tests: XCTestCase {
       ]}
     }
     let object: JSONObject = ["name": "Luke Skywalker"]
-    let variables = ["variable": true].toInputVariables()
+    let variables = ["variable": true]
 
     // when
     let data = try readValues(GivenSelectionSet.self, from: object, variables: variables)
@@ -1188,7 +1188,7 @@ class GraphQLExecutor_SelectionSetMapper_FromResponse_Tests: XCTestCase {
       ]}
     }
     let object: JSONObject = ["name": "Luke Skywalker", "id": "1234"]
-    let variables = ["variable": false].toInputVariables()
+    let variables = ["variable": false]
 
     // when
     let data = try readValues(GivenSelectionSet.self, from: object, variables: variables)
@@ -1209,7 +1209,7 @@ class GraphQLExecutor_SelectionSetMapper_FromResponse_Tests: XCTestCase {
       ]}
     }
     let object: JSONObject = ["name": "Luke Skywalker", "id": "1234"]
-    let variables = ["variable": true].toInputVariables()
+    let variables = ["variable": true]
 
     // when
     let data = try readValues(GivenSelectionSet.self, from: object, variables: variables)
@@ -1234,7 +1234,7 @@ class GraphQLExecutor_SelectionSetMapper_FromResponse_Tests: XCTestCase {
       ]}
     }
     let object: JSONObject = ["name": "Luke Skywalker"]
-    let variables = ["variable": true].toInputVariables()
+    let variables = ["variable": true]
 
     // when
     let data = try readValues(GivenSelectionSet.self, from: object, variables: variables)
@@ -1259,7 +1259,7 @@ class GraphQLExecutor_SelectionSetMapper_FromResponse_Tests: XCTestCase {
     }
     let object: JSONObject = ["name": "Luke Skywalker", "id": "1234"]
     let variables = ["skip": true,
-                     "include": true].toInputVariables()
+                     "include": true]
 
     // when
     let data = try readValues(GivenSelectionSet.self, from: object, variables: variables)
@@ -1282,7 +1282,7 @@ class GraphQLExecutor_SelectionSetMapper_FromResponse_Tests: XCTestCase {
     }
     let object: JSONObject = ["name": "Luke Skywalker", "id": "1234"]
     let variables = ["skip": true,
-                     "include": false].toInputVariables()
+                     "include": false]
 
     // when
     let data = try readValues(GivenSelectionSet.self, from: object, variables: variables)
@@ -1305,7 +1305,7 @@ class GraphQLExecutor_SelectionSetMapper_FromResponse_Tests: XCTestCase {
     }
     let object: JSONObject = ["name": "Luke Skywalker", "id": "1234"]
     let variables = ["skip": false,
-                     "include": false].toInputVariables()
+                     "include": false]
 
     // when
     let data = try readValues(GivenSelectionSet.self, from: object, variables: variables)
@@ -1328,7 +1328,7 @@ class GraphQLExecutor_SelectionSetMapper_FromResponse_Tests: XCTestCase {
     }
     let object: JSONObject = ["name": "Luke Skywalker", "id": "1234"]
     let variables = ["skip": false,
-                     "include": true].toInputVariables()
+                     "include": true]
 
     // when
     let data = try readValues(GivenSelectionSet.self, from: object, variables: variables)
@@ -1348,7 +1348,7 @@ class GraphQLExecutor_SelectionSetMapper_FromResponse_Tests: XCTestCase {
     }
     let object: JSONObject = ["name": "Luke Skywalker", "id": "1234"]
     let variables = ["skip": true,
-                     "include": true].toInputVariables()
+                     "include": true]
 
     // when
     let data = try readValues(GivenSelectionSet.self, from: object, variables: variables)
@@ -1367,7 +1367,7 @@ class GraphQLExecutor_SelectionSetMapper_FromResponse_Tests: XCTestCase {
     }
     let object: JSONObject = ["name": "Luke Skywalker", "id": "1234"]
     let variables = ["skip": false,
-                     "include": false].toInputVariables()
+                     "include": false]
 
     // when
     let data = try readValues(GivenSelectionSet.self, from: object, variables: variables)
@@ -1386,7 +1386,7 @@ class GraphQLExecutor_SelectionSetMapper_FromResponse_Tests: XCTestCase {
     }
     let object: JSONObject = ["name": "Luke Skywalker", "id": "1234"]
     let variables = ["skip": false,
-                     "include": true].toInputVariables()
+                     "include": true]
 
     // when
     let data = try readValues(GivenSelectionSet.self, from: object, variables: variables)
@@ -1405,7 +1405,7 @@ class GraphQLExecutor_SelectionSetMapper_FromResponse_Tests: XCTestCase {
     }
     let object: JSONObject = ["name": "Luke Skywalker", "id": "1234"]
     let variables = ["skip": true,
-                     "include": false].toInputVariables()
+                     "include": false]
 
     // when
     let data = try readValues(GivenSelectionSet.self, from: object, variables: variables)
diff --git a/Tests/ApolloTests/GraphQLMapEncodingTests.swift b/Tests/ApolloTests/GraphQLMapEncodingTests.swift
index 0f52ba39a8..acf896d773 100644
--- a/Tests/ApolloTests/GraphQLMapEncodingTests.swift
+++ b/Tests/ApolloTests/GraphQLMapEncodingTests.swift
@@ -6,9 +6,9 @@ import StarWarsAPI
 
 #warning("TODO: Do we refactor these for [String: InputValue] or delete them?")
 class GraphQLMapEncodingTests: XCTestCase {
-  private struct MockGraphQLMapConvertible: GraphQLMapConvertible {
-    let graphQLMap: GraphQLMap
-  }
+//  private struct MockGraphQLMapConvertible: GraphQLMapConvertible {
+//    let graphQLMap: GraphQLMap
+//  }
   
 //  private func serializeAndDeserialize(_ map: GraphQLMap) -> NSDictionary {
 //    let input = MockGraphQLMapConvertible(graphQLMap: map)
diff --git a/Tests/ApolloTests/JSONValueMatcher.swift b/Tests/ApolloTests/JSONValueMatcher.swift
index 10e0b121d6..047f075a98 100644
--- a/Tests/ApolloTests/JSONValueMatcher.swift
+++ b/Tests/ApolloTests/JSONValueMatcher.swift
@@ -36,7 +36,7 @@ public func equalJSONValue(_ expectedValue: JSONEncodable?) -> Predicate<JSONEnc
   }
 }
 
-public func equal(_ expectedValue: GraphQLMap?) -> Predicate<GraphQLMap> {
+public func equal(_ expectedValue: JSONEncodableDictionary?) -> Predicate<JSONEncodableDictionary> {
   return Predicate { actual in
     let msg = ExpectationMessage.expectedActualValueTo("equal <\(stringify(expectedValue))>")
     if let actualValue = try actual.evaluate(), let expectedValue = expectedValue {
diff --git a/Tests/ApolloTests/RequestBodyCreatorTests.swift b/Tests/ApolloTests/RequestBodyCreatorTests.swift
index d0c92b87cd..e01d6cf3d5 100644
--- a/Tests/ApolloTests/RequestBodyCreatorTests.swift
+++ b/Tests/ApolloTests/RequestBodyCreatorTests.swift
@@ -14,7 +14,10 @@ import ApolloTestSupport
 
 class RequestBodyCreatorTests: XCTestCase {
 
-  func create<Operation: GraphQLOperation>(with creator: RequestBodyCreator, for operation: Operation) -> GraphQLMap {
+  func create<Operation: GraphQLOperation>(
+    with creator: RequestBodyCreator,
+    for operation: Operation
+  ) -> JSONEncodableDictionary {
     creator.requestBody(for: operation,
                         sendOperationIdentifiers: false,
                         sendQueryDocument: true,
@@ -53,6 +56,10 @@ class RequestBodyCreatorTests: XCTestCase {
     expect(actual).to(equalJSONValue(expected))
   }
 
-  #warning("TODO: Test generated input objects converted to variables correctly.")
+  #warning("""
+TODO: Test generated input objects converted to variables correctly.
+- nil variable value
+- null variable value
+""")
 }
 
diff --git a/Tests/ApolloTests/TestCustomRequestBodyCreator.swift b/Tests/ApolloTests/TestCustomRequestBodyCreator.swift
index 4a11d3824b..48e349f5b2 100644
--- a/Tests/ApolloTests/TestCustomRequestBodyCreator.swift
+++ b/Tests/ApolloTests/TestCustomRequestBodyCreator.swift
@@ -11,13 +11,13 @@ import ApolloAPI
 
 struct TestCustomRequestBodyCreator: RequestBodyCreator {
 
-  var stubbedRequestBody: GraphQLMap = ["TestCustomRequestBodyCreator": "TestBodyValue"]
+  var stubbedRequestBody: JSONEncodableDictionary = ["TestCustomRequestBodyCreator": "TestBodyValue"]
 
   func requestBody<Operation: GraphQLOperation>(
     for operation: Operation,
     sendOperationIdentifiers: Bool,
     sendQueryDocument: Bool, autoPersistQuery: Bool
-  ) -> GraphQLMap {
+  ) -> JSONEncodableDictionary {
     stubbedRequestBody
   }
 }
diff --git a/Tests/ApolloTests/WebSocket/WebSocketTests.swift b/Tests/ApolloTests/WebSocket/WebSocketTests.swift
index 6688f91988..714a7f5321 100644
--- a/Tests/ApolloTests/WebSocket/WebSocketTests.swift
+++ b/Tests/ApolloTests/WebSocket/WebSocketTests.swift
@@ -6,7 +6,7 @@ import ApolloTestSupport
 @testable import ApolloWebSocket
 
 extension WebSocketTransport {
-  func write(message: GraphQLMap) {
+  func write(message: JSONEncodableDictionary) {
     let serialized = try! JSONSerializationFormat.serialize(value: message)
     if let str = String(data: serialized, encoding: .utf8) {
       self.websocket.write(string: str)
@@ -72,7 +72,7 @@ class WebSocketTests: XCTestCase {
       }
     }
         
-    let message : GraphQLMap = [
+    let message : JSONEncodableDictionary = [
       "type": "data",
       "id": "1",
       "payload": [
@@ -127,7 +127,7 @@ class WebSocketTests: XCTestCase {
       }
     }
     
-    let message : GraphQLMap = [
+    let message : JSONEncodableDictionary = [
       "type": "data",
       "id": "2",            // subscribing on id = 1, i.e. expecting error when receiving id = 2
       "payload": [
@@ -170,7 +170,7 @@ class WebSocketTests: XCTestCase {
       }
     }
     
-    let message : GraphQLMap = [
+    let message : JSONEncodableDictionary = [
       "type": "data",
       "id": "12345678", // subscribing on id = 12345678 from custom operation id
       "payload": [