diff --git a/Source/ARTBaseMessage.h b/Source/ARTBaseMessage.h
index e8a485e68..94b4dc481 100644
--- a/Source/ARTBaseMessage.h
+++ b/Source/ARTBaseMessage.h
@@ -22,7 +22,7 @@ NS_ASSUME_NONNULL_BEGIN
 
 @property (strong, nonatomic, nullable) id data;
 
-@property (nullable, nonatomic) id<ARTJsonCompatible> extras;
+@property (strong, nullable, nonatomic) id<ARTJsonCompatible> extras;
 
 - (NSString *)description;
 
diff --git a/Source/ARTDeviceDetails.h b/Source/ARTDeviceDetails.h
index e772ecef4..623ba62ff 100644
--- a/Source/ARTDeviceDetails.h
+++ b/Source/ARTDeviceDetails.h
@@ -7,12 +7,12 @@ NS_ASSUME_NONNULL_BEGIN
 
 @interface ARTDeviceDetails : NSObject
 
-@property (nonatomic) ARTDeviceId *id;
-@property (nullable, nonatomic) NSString *clientId;
-@property (nonatomic) NSString *platform;
-@property (nonatomic) NSString *formFactor;
-@property (nonatomic) NSMutableDictionary<NSString *, NSString *> *metadata;
-@property (nonatomic) ARTDevicePushDetails *push;
+@property (strong, nonatomic) ARTDeviceId *id;
+@property (strong, nullable, nonatomic) NSString *clientId;
+@property (strong, nonatomic) NSString *platform;
+@property (strong, nonatomic) NSString *formFactor;
+@property (strong, nonatomic) NSDictionary<NSString *, NSString *> *metadata;
+@property (strong, nonatomic) ARTDevicePushDetails *push;
 
 - (instancetype)init;
 - (instancetype)initWithId:(ARTDeviceId *)deviceId;
diff --git a/Source/ARTDeviceDetails.m b/Source/ARTDeviceDetails.m
index 132c2cc57..03e640bb3 100644
--- a/Source/ARTDeviceDetails.m
+++ b/Source/ARTDeviceDetails.m
@@ -6,7 +6,7 @@ @implementation ARTDeviceDetails
 - (instancetype)init {
     if (self = [super init]) {
         _push = [[ARTDevicePushDetails alloc] init];
-        _metadata = [[NSMutableDictionary alloc] init];
+        _metadata = [[NSDictionary alloc] init];
     }
     return self;
 }
@@ -21,10 +21,10 @@ - (instancetype)initWithId:(ARTDeviceId *)deviceId {
 - (id)copyWithZone:(NSZone *)zone {
     ARTDeviceDetails *device = [[[self class] allocWithZone:zone] init];
 
-    device.id = self.id;
-    device.clientId = self.clientId;
-    device.platform = self.platform;
-    device.formFactor = self.formFactor;
+    device.id = [self.id copy];
+    device.clientId = [self.clientId copy];
+    device.platform = [self.platform copy];
+    device.formFactor = [self.formFactor copy];
     device.metadata = [self.metadata copy];
     device.push = [self.push copy];
 
diff --git a/Source/ARTDevicePushDetails.h b/Source/ARTDevicePushDetails.h
index 18de18e92..66556fc17 100644
--- a/Source/ARTDevicePushDetails.h
+++ b/Source/ARTDevicePushDetails.h
@@ -6,9 +6,9 @@ NS_ASSUME_NONNULL_BEGIN
 
 @interface ARTDevicePushDetails : NSObject
 
-@property (nonatomic) NSMutableDictionary<NSString *, NSString *> *recipient;
-@property (nullable, nonatomic) NSString *state;
-@property (nullable, nonatomic) ARTErrorInfo *errorReason;
+@property (strong, nonatomic) NSMutableDictionary<NSString *, NSString *> *recipient;
+@property (strong, nullable, nonatomic) NSString *state;
+@property (strong, nullable, nonatomic) ARTErrorInfo *errorReason;
 
 - (instancetype)init;
 
diff --git a/Source/ARTLocalDevice.h b/Source/ARTLocalDevice.h
index 1c7e4a726..866bf1240 100644
--- a/Source/ARTLocalDevice.h
+++ b/Source/ARTLocalDevice.h
@@ -12,7 +12,7 @@ NS_ASSUME_NONNULL_BEGIN
 /**
  Device secret generated using random data with sufficient entropy. It's a sha256 digest encoded with base64.
  */
-@property (nullable, nonatomic) ARTDeviceSecret *secret;
+@property (strong, nullable, nonatomic) ARTDeviceSecret *secret;
 
 - (instancetype)init NS_UNAVAILABLE;
 
diff --git a/Source/ARTPresenceMap.h b/Source/ARTPresenceMap.h
index 3f8c1c416..6b358035b 100644
--- a/Source/ARTPresenceMap.h
+++ b/Source/ARTPresenceMap.h
@@ -29,7 +29,7 @@ NS_ASSUME_NONNULL_BEGIN
 @property (nullable, weak) id<ARTPresenceMapDelegate> delegate; // weak because delegates outlive their counterpart
 
 @property (readwrite, nonatomic, assign) int64_t syncMsgSerial;
-@property (readwrite, nonatomic, nullable) NSString *syncChannelSerial;
+@property (strong, readwrite, nonatomic, nullable) NSString *syncChannelSerial;
 @property (readonly, nonatomic, assign) NSUInteger syncSessionId;
 @property (readonly, nonatomic, getter=syncComplete) BOOL syncComplete;
 @property (readonly, nonatomic, getter=syncInProgress) BOOL syncInProgress;
diff --git a/Source/ARTProtocolMessage.h b/Source/ARTProtocolMessage.h
index 31c6fe651..8ae70d440 100644
--- a/Source/ARTProtocolMessage.h
+++ b/Source/ARTProtocolMessage.h
@@ -55,8 +55,8 @@ NS_ASSUME_NONNULL_BEGIN
 @property (nullable, readwrite, strong, nonatomic) NSArray<ARTMessage *> *messages;
 @property (nullable, readwrite, strong, nonatomic) NSArray<ARTPresenceMessage *> *presence;
 @property (readwrite, assign, nonatomic) int64_t flags;
-@property (nullable, readwrite, nonatomic) ARTConnectionDetails *connectionDetails;
-@property (nullable, nonatomic) ARTAuthDetails *auth;
+@property (strong, nullable, readwrite, nonatomic) ARTConnectionDetails *connectionDetails;
+@property (strong, nullable, nonatomic) ARTAuthDetails *auth;
 @property (nonatomic, strong, nullable) NSStringDictionary *params;
 
 @end
diff --git a/Spec/Tests/PushAdminTests.swift b/Spec/Tests/PushAdminTests.swift
index 5c2545efb..22a6e7c4f 100644
--- a/Spec/Tests/PushAdminTests.swift
+++ b/Spec/Tests/PushAdminTests.swift
@@ -26,7 +26,7 @@ class PushAdminTests: XCTestCase {
         let deviceDetails = ARTDeviceDetails(id: "testDeviceDetails")
         deviceDetails.platform = "ios"
         deviceDetails.formFactor = "phone"
-        deviceDetails.metadata = NSMutableDictionary()
+        deviceDetails.metadata = [String : String]()
         deviceDetails.push.recipient = [
             "transportType": "apns",
             "deviceToken": "foo",
@@ -39,7 +39,7 @@ class PushAdminTests: XCTestCase {
         deviceDetails.platform = "android"
         deviceDetails.formFactor = "tablet"
         deviceDetails.clientId = "clientA"
-        deviceDetails.metadata = NSMutableDictionary()
+        deviceDetails.metadata = [String : String]()
         deviceDetails.push.recipient = [
             "transportType": "gcm",
             "registrationToken": "qux",
@@ -52,7 +52,7 @@ class PushAdminTests: XCTestCase {
         deviceDetails.platform = "android"
         deviceDetails.formFactor = "tablet"
         deviceDetails.clientId = "clientA"
-        deviceDetails.metadata = NSMutableDictionary()
+        deviceDetails.metadata = [String : String]()
         deviceDetails.push.recipient = [
             "transportType": "gcm",
             "registrationToken": "qux",
@@ -65,7 +65,7 @@ class PushAdminTests: XCTestCase {
         deviceDetails.platform = "android"
         deviceDetails.formFactor = "tablet"
         deviceDetails.clientId = "clientB"
-        deviceDetails.metadata = NSMutableDictionary()
+        deviceDetails.metadata = [String : String]()
         deviceDetails.push.recipient = [
             "transportType": "gcm",
             "registrationToken": "qux",