diff --git a/examples/client/gradle-client/build.gradle.kts b/examples/client/gradle-client/build.gradle.kts
index 952c502bfd..b2b1a27f04 100644
--- a/examples/client/gradle-client/build.gradle.kts
+++ b/examples/client/gradle-client/build.gradle.kts
@@ -3,7 +3,7 @@ import com.expediagroup.graphql.plugin.gradle.graphql
 
 plugins {
     application
-    id("org.jetbrains.kotlin.jvm") version "1.3.72"
+    id("org.jetbrains.kotlin.jvm") version "1.4.0"
     id("com.expediagroup.graphql") version "3.1.0"
 }
 
diff --git a/examples/client/maven-client/pom.xml b/examples/client/maven-client/pom.xml
index 95e436c7a3..21e59a305c 100755
--- a/examples/client/maven-client/pom.xml
+++ b/examples/client/maven-client/pom.xml
@@ -10,8 +10,8 @@
         <!-- those properties are set by gradle -->
         <graphql-kotlin.version>3.1.0</graphql-kotlin.version>
         <!-- lib versions -->
-        <kotlin.version>1.3.72</kotlin.version>
-        <kotlin-coroutines.version>1.3.6</kotlin-coroutines.version>
+        <kotlin.version>1.4.0</kotlin.version>
+        <kotlin-coroutines.version>1.3.9</kotlin-coroutines.version>
         <ktor.version>1.3.1</ktor.version>
     </properties>
 
diff --git a/examples/client/server/build.gradle.kts b/examples/client/server/build.gradle.kts
index 2542cea0a3..c84568d4a9 100644
--- a/examples/client/server/build.gradle.kts
+++ b/examples/client/server/build.gradle.kts
@@ -1,6 +1,6 @@
 plugins {
-    id("org.jetbrains.kotlin.jvm") version "1.3.72"
-    id("org.jetbrains.kotlin.plugin.spring") version "1.3.72"
+    id("org.jetbrains.kotlin.jvm") version "1.4.0"
+    id("org.jetbrains.kotlin.plugin.spring") version "1.4.0"
     id("org.springframework.boot") version "2.2.7.RELEASE"
 }
 
diff --git a/gradle.properties b/gradle.properties
index c2018c3e17..4eab5e7acc 100644
--- a/gradle.properties
+++ b/gradle.properties
@@ -15,8 +15,8 @@ org.gradle.jvmargs=-Xmx2g -XX:MaxPermSize=512m -XX:+HeapDumpOnOutOfMemoryError
 
 # dependencies
 kotlinJvmVersion = 1.8
-kotlinVersion = 1.3.72
-kotlinCoroutinesVersion = 1.3.7
+kotlinVersion = 1.4.0
+kotlinCoroutinesVersion = 1.3.9
 
 classGraphVersion = 4.8.87
 graphQLJavaVersion = 15.0
diff --git a/graphql-kotlin-schema-generator/src/main/kotlin/com/expediagroup/graphql/generator/extensions/kTypeExtensions.kt b/graphql-kotlin-schema-generator/src/main/kotlin/com/expediagroup/graphql/generator/extensions/kTypeExtensions.kt
index 5f24c9ef8a..9664fdbdbe 100644
--- a/graphql-kotlin-schema-generator/src/main/kotlin/com/expediagroup/graphql/generator/extensions/kTypeExtensions.kt
+++ b/graphql-kotlin-schema-generator/src/main/kotlin/com/expediagroup/graphql/generator/extensions/kTypeExtensions.kt
@@ -21,7 +21,6 @@ import kotlin.reflect.KClass
 import kotlin.reflect.KType
 import kotlin.reflect.full.createType
 import kotlin.reflect.full.isSubclassOf
-import kotlin.reflect.jvm.javaType
 import kotlin.reflect.jvm.jvmErasure
 
 private val primitiveArrayTypes = mapOf(
@@ -36,7 +35,7 @@ private val primitiveArrayTypes = mapOf(
 
 internal fun KType.getKClass() = this.jvmErasure
 
-internal fun KType.getJavaClass() = this.javaType as Class<*>
+internal fun KType.getJavaClass(): Class<*> = this.getKClass().java
 
 internal fun KType.isSubclassOf(kClass: KClass<*>) = this.getKClass().isSubclassOf(kClass)
 
diff --git a/graphql-kotlin-schema-generator/src/test/kotlin/com/expediagroup/graphql/directives/KotlinDirectiveWiringFactoryTest.kt b/graphql-kotlin-schema-generator/src/test/kotlin/com/expediagroup/graphql/directives/KotlinDirectiveWiringFactoryTest.kt
index a860703e3f..eab8a1c8a0 100644
--- a/graphql-kotlin-schema-generator/src/test/kotlin/com/expediagroup/graphql/directives/KotlinDirectiveWiringFactoryTest.kt
+++ b/graphql-kotlin-schema-generator/src/test/kotlin/com/expediagroup/graphql/directives/KotlinDirectiveWiringFactoryTest.kt
@@ -211,7 +211,7 @@ class KotlinDirectiveWiringFactoryTest {
     }
 
     @Test
-    fun `verify exception is thrown if no coordinates or code registry is specified for the field`() {
+    fun `verify exception is thrown if no coordinates are specified for the field`() {
         val myTestField = GraphQLFieldDefinition.newFieldDefinition()
             .name("MyField")
             .type { context, visitor -> context.thisNode().accept(context, visitor) }
@@ -220,7 +220,21 @@ class KotlinDirectiveWiringFactoryTest {
             .build()
 
         assertFailsWith(InvalidSchemaDirectiveWiringException::class) {
-            SimpleWiringFactory().onWire(graphQLSchemaElement = myTestField, coordinates = null, codeRegistry = null)
+            SimpleWiringFactory().onWire(graphQLSchemaElement = myTestField, coordinates = null, codeRegistry = mockk())
+        }
+    }
+
+    @Test
+    fun `verify exception is thrown if no code registry is specified for the field`() {
+        val myTestField = GraphQLFieldDefinition.newFieldDefinition()
+            .name("MyField")
+            .type { context, visitor -> context.thisNode().accept(context, visitor) }
+            .description("My Field Description")
+            .withDirective(graphQLLowercaseDirective)
+            .build()
+
+        assertFailsWith(InvalidSchemaDirectiveWiringException::class) {
+            SimpleWiringFactory().onWire(graphQLSchemaElement = myTestField, coordinates = mockk(), codeRegistry = null)
         }
     }
 
diff --git a/graphql-kotlin-schema-generator/src/test/kotlin/com/expediagroup/graphql/generator/extensions/KTypeExtensionsKtTest.kt b/graphql-kotlin-schema-generator/src/test/kotlin/com/expediagroup/graphql/generator/extensions/KTypeExtensionsKtTest.kt
index e0cf5aaa11..f70016e131 100644
--- a/graphql-kotlin-schema-generator/src/test/kotlin/com/expediagroup/graphql/generator/extensions/KTypeExtensionsKtTest.kt
+++ b/graphql-kotlin-schema-generator/src/test/kotlin/com/expediagroup/graphql/generator/extensions/KTypeExtensionsKtTest.kt
@@ -25,16 +25,18 @@ import org.junit.jupiter.api.condition.EnabledOnJre
 import org.junit.jupiter.api.condition.JRE
 import kotlin.reflect.KType
 import kotlin.reflect.KTypeProjection
+import kotlin.reflect.full.createType
 import kotlin.reflect.full.findParameterByName
 import kotlin.reflect.full.starProjectedType
 import kotlin.test.assertEquals
 import kotlin.test.assertFailsWith
 import kotlin.test.assertFalse
+import kotlin.test.assertNotNull
 import kotlin.test.assertTrue
 
-internal class KTypeExtensionsKtTest {
+class KTypeExtensionsKtTest {
 
-    internal class MyClass {
+    class MyClass {
         fun listFun(list: List<String>) = list.joinToString(separator = ",") { it }
 
         fun arrayFun(array: Array<String>) = array.joinToString(separator = ",") { it }
@@ -44,9 +46,9 @@ internal class KTypeExtensionsKtTest {
         fun stringFun(string: String) = "hello $string"
     }
 
-    internal interface SimpleInterface
+    interface SimpleInterface
 
-    internal class SimpleClass(val id: String) : SimpleInterface
+    class SimpleClass(val id: String) : SimpleInterface
 
     @Test
     fun getTypeOfFirstArgument() {
@@ -77,7 +79,22 @@ internal class KTypeExtensionsKtTest {
 
     @Test
     fun getKClass() {
-        assertEquals(MyClass::class, MyClass::class.starProjectedType.getKClass())
+        assertEquals(MyClass::class, MyClass::class.createType().getKClass())
+    }
+
+    @Test
+    fun getJavaClass() {
+        val listType = assertNotNull(MyClass::listFun.findParameterByName("list")?.type)
+        assertEquals(List::class.java, listType.getJavaClass())
+
+        val arrayType = assertNotNull(MyClass::arrayFun.findParameterByName("array")?.type)
+        assertEquals(Array<String>::class.java, arrayType.getJavaClass())
+
+        val primitiveArrayType = assertNotNull(MyClass::primitiveArrayFun.findParameterByName("intArray")?.type)
+        assertEquals(IntArray::class.java, primitiveArrayType.getJavaClass())
+
+        val stringType = assertNotNull(MyClass::stringFun.findParameterByName("string")?.type)
+        assertEquals(String::class.java, stringType.getJavaClass())
     }
 
     @Test
diff --git a/graphql-kotlin-schema-generator/src/test/kotlin/com/expediagroup/graphql/generator/types/GenerateDirectiveTest.kt b/graphql-kotlin-schema-generator/src/test/kotlin/com/expediagroup/graphql/generator/types/GenerateDirectiveTest.kt
index 224bb7b9c5..177e9dd817 100644
--- a/graphql-kotlin-schema-generator/src/test/kotlin/com/expediagroup/graphql/generator/types/GenerateDirectiveTest.kt
+++ b/graphql-kotlin-schema-generator/src/test/kotlin/com/expediagroup/graphql/generator/types/GenerateDirectiveTest.kt
@@ -26,6 +26,7 @@ import com.expediagroup.graphql.test.utils.SimpleDirective
 import org.junit.jupiter.api.AfterAll
 import org.junit.jupiter.api.Test
 import kotlin.reflect.KClass
+import kotlin.reflect.KFunction
 import kotlin.test.assertEquals
 import kotlin.test.assertTrue
 
@@ -92,40 +93,47 @@ class GenerateDirectiveTest {
 
     @Test
     fun `no annotation`() {
-        assertTrue(generateDirectives(basicGenerator, MyClass::noAnnotation).isEmpty().isTrue())
+        val noAnnotation: KFunction<String> = MyClass::noAnnotation
+        assertTrue(generateDirectives(basicGenerator, noAnnotation).isEmpty().isTrue())
     }
 
     @Test
     fun `no directive`() {
-        assertTrue(generateDirectives(basicGenerator, MyClass::noDirective).isEmpty().isTrue())
+        val noDirective: KFunction<String> = MyClass::noDirective
+        assertTrue(generateDirectives(basicGenerator, noDirective).isEmpty().isTrue())
     }
 
     @Test
     fun `has directive`() {
-        assertEquals(expected = 1, actual = generateDirectives(basicGenerator, MyClass::simpleDirective).size)
+        val simpleDirective: KFunction<String> = MyClass::simpleDirective
+        assertEquals(expected = 1, actual = generateDirectives(basicGenerator, simpleDirective).size)
     }
 
     @Test
     fun `has directive with string`() {
-        assertEquals(expected = 1, actual = generateDirectives(basicGenerator, MyClass::directiveWithString).size)
+        val directiveWithString: KFunction<String> = MyClass::directiveWithString
+        assertEquals(expected = 1, actual = generateDirectives(basicGenerator, directiveWithString).size)
     }
 
     @Test
     fun `has directive with enum`() {
-        assertEquals(expected = 1, actual = generateDirectives(basicGenerator, MyClass::directiveWithEnum).size)
+        val directiveWithEnum: KFunction<String> = MyClass::directiveWithEnum
+        assertEquals(expected = 1, actual = generateDirectives(basicGenerator, directiveWithEnum).size)
     }
 
     @Test
     fun `has directive with class`() {
-        assertEquals(expected = 1, actual = generateDirectives(basicGenerator, MyClass::directiveWithClass).size)
+        val directiveWithClass: KFunction<String> = MyClass::directiveWithClass
+        assertEquals(expected = 1, actual = generateDirectives(basicGenerator, directiveWithClass).size)
     }
 
     @Test
     fun `directives are only added to the schema once`() {
         val initialCount = basicGenerator.directives.size
-        val firstInvocation = generateDirectives(basicGenerator, MyClass::simpleDirective)
+        val simpleDirective: KFunction<String> = MyClass::simpleDirective
+        val firstInvocation = generateDirectives(basicGenerator, simpleDirective)
         assertEquals(1, firstInvocation.size)
-        val secondInvocation = generateDirectives(basicGenerator, MyClass::simpleDirective)
+        val secondInvocation = generateDirectives(basicGenerator, simpleDirective)
         assertEquals(1, secondInvocation.size)
         assertEquals(firstInvocation.first(), secondInvocation.first())
         assertEquals(initialCount + 1, basicGenerator.directives.size)
@@ -154,8 +162,10 @@ class GenerateDirectiveTest {
     @Test
     fun `directives are created per each declaration`() {
         val initialCount = basicGenerator.directives.size
-        val directivesOnFirstField = generateDirectives(basicGenerator, MyClass::directiveWithString)
-        val directivesOnSecondField = generateDirectives(basicGenerator, MyClass::directiveWithAnotherString)
+        val directiveWithString: KFunction<String> = MyClass::directiveWithString
+        val directiveWithAnotherString: KFunction<String> = MyClass::directiveWithAnotherString
+        val directivesOnFirstField = generateDirectives(basicGenerator, directiveWithString)
+        val directivesOnSecondField = generateDirectives(basicGenerator, directiveWithAnotherString)
         assertEquals(expected = 1, actual = directivesOnFirstField.size)
         assertEquals(expected = 1, actual = directivesOnSecondField.size)
 
@@ -191,7 +201,8 @@ class GenerateDirectiveTest {
 
     @Test
     fun `exlude directive arguments @GraphQLIgnore`() {
-        val directives = generateDirectives(basicGenerator, MyClass::directiveWithIgnoredArgs)
+        val directiveWithIgnoredArgs: KFunction<String> = MyClass::directiveWithIgnoredArgs
+        val directives = generateDirectives(basicGenerator, directiveWithIgnoredArgs)
         assertEquals(expected = 1, actual = directives.size)
         assertEquals(expected = 1, actual = directives.first().arguments.size)
         assertEquals(expected = "string", actual = directives.first().arguments.first().name)
diff --git a/graphql-kotlin-schema-generator/src/test/kotlin/com/expediagroup/graphql/hooks/FlowSubscriptionSchemaGeneratorHooksTest.kt b/graphql-kotlin-schema-generator/src/test/kotlin/com/expediagroup/graphql/hooks/FlowSubscriptionSchemaGeneratorHooksTest.kt
new file mode 100644
index 0000000000..9133f3b5e5
--- /dev/null
+++ b/graphql-kotlin-schema-generator/src/test/kotlin/com/expediagroup/graphql/hooks/FlowSubscriptionSchemaGeneratorHooksTest.kt
@@ -0,0 +1,62 @@
+/*
+ * Copyright 2020 Expedia, Inc
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.expediagroup.graphql.hooks
+
+import kotlinx.coroutines.flow.Flow
+import kotlinx.coroutines.flow.emptyFlow
+import org.junit.jupiter.api.Test
+import java.util.concurrent.CompletableFuture
+import kotlin.reflect.full.createType
+import kotlin.reflect.jvm.reflect
+import kotlin.test.assertEquals
+import kotlin.test.assertFalse
+import kotlin.test.assertNotNull
+import kotlin.test.assertTrue
+
+class FlowSubscriptionSchemaGeneratorHooksTest {
+
+    val hooks = FlowSubscriptionSchemaGeneratorHooks()
+
+    @Test
+    fun `willResolveMonad unwraps Flow`() {
+        val type = assertNotNull(TestQuery::getFlow.reflect()?.returnType)
+        val result = hooks.willResolveMonad(type)
+        assertEquals(String::class.createType(), result)
+    }
+
+    @Test
+    fun `willResolveMonad does nothing on any other type`() {
+        val stringType = assertNotNull(TestQuery::getString.reflect()?.returnType)
+        val cfType = assertNotNull(TestQuery::getCompletableFuture.reflect()?.returnType)
+
+        assertEquals(stringType, hooks.willResolveMonad(stringType))
+        assertEquals(cfType, hooks.willResolveMonad(cfType))
+    }
+
+    @Test
+    fun isValidSubscriptionReturnType() {
+        assertTrue(hooks.isValidSubscriptionReturnType(TestQuery::class, TestQuery::getFlow))
+        assertFalse(hooks.isValidSubscriptionReturnType(TestQuery::class, TestQuery::getString))
+        assertFalse(hooks.isValidSubscriptionReturnType(TestQuery::class, TestQuery::getCompletableFuture))
+    }
+
+    class TestQuery {
+        fun getFlow(): Flow<String> = emptyFlow()
+        fun getString(): String = ""
+        fun getCompletableFuture(): CompletableFuture<String> = CompletableFuture.completedFuture("")
+    }
+}
diff --git a/graphql-kotlin-schema-generator/src/test/kotlin/com/expediagroup/graphql/hooks/SchemaGeneratorHooksTest.kt b/graphql-kotlin-schema-generator/src/test/kotlin/com/expediagroup/graphql/hooks/SchemaGeneratorHooksTest.kt
index 774bfbf96c..3bbef2ee93 100644
--- a/graphql-kotlin-schema-generator/src/test/kotlin/com/expediagroup/graphql/hooks/SchemaGeneratorHooksTest.kt
+++ b/graphql-kotlin-schema-generator/src/test/kotlin/com/expediagroup/graphql/hooks/SchemaGeneratorHooksTest.kt
@@ -302,7 +302,7 @@ class SchemaGeneratorHooksTest {
     @Test
     fun `willResolveMonad returns basic type`() {
         val hooks = NoopSchemaGeneratorHooks
-        val type = TestQuery::query.returnType
+        val type = (TestQuery::query as KFunction<*>).returnType
 
         assertEquals(expected = "SomeData", actual = hooks.willResolveMonad(type).getSimpleName())
     }
diff --git a/plugins/graphql-kotlin-gradle-plugin/src/test/kotlin/com/expediagroup/graphql/plugin/gradle/GraphQLGradlePluginAbstractIT.kt b/plugins/graphql-kotlin-gradle-plugin/src/test/kotlin/com/expediagroup/graphql/plugin/gradle/GraphQLGradlePluginAbstractIT.kt
index 4c717f8f18..81a184d348 100755
--- a/plugins/graphql-kotlin-gradle-plugin/src/test/kotlin/com/expediagroup/graphql/plugin/gradle/GraphQLGradlePluginAbstractIT.kt
+++ b/plugins/graphql-kotlin-gradle-plugin/src/test/kotlin/com/expediagroup/graphql/plugin/gradle/GraphQLGradlePluginAbstractIT.kt
@@ -34,8 +34,8 @@ abstract class GraphQLGradlePluginAbstractIT {
 
     // unsure if there is a better way - correct values are set from Gradle build
     // when running directly from IDE you will need to manually update those to correct values
-    private val gqlKotlinVersion = System.getProperty("graphQLKotlinVersion") ?: "3.0.0-SNAPSHOT"
-    private val kotlinVersion = System.getProperty("kotlinVersion") ?: "1.3.72"
+    private val gqlKotlinVersion = System.getProperty("graphQLKotlinVersion") ?: "4.0.0-SNAPSHOT"
+    private val kotlinVersion = System.getProperty("kotlinVersion") ?: "1.4.0"
     private val junitVersion = System.getProperty("junitVersion") ?: "5.6.2"
 
     val testSchema = loadResource("mocks/schema.graphql")