diff --git a/ably-ios/ARTConnection.m b/ably-ios/ARTConnection.m
index 130ae7600..7d0efa76a 100644
--- a/ably-ios/ARTConnection.m
+++ b/ably-ios/ARTConnection.m
@@ -26,6 +26,7 @@ - (instancetype)initWithRealtime:(ARTRealtime *)realtime {
     if (self == [super init]) {
         _realtime = realtime;
         _eventEmitter = realtime.eventEmitter;
+        _serial = -1;
     }
     return self;
 }
diff --git a/ablySpec/RealtimeClientConnection.swift b/ablySpec/RealtimeClientConnection.swift
index 0e612344d..ccd21c522 100644
--- a/ablySpec/RealtimeClientConnection.swift
+++ b/ablySpec/RealtimeClientConnection.swift
@@ -952,7 +952,7 @@ class RealtimeClientConnection: QuickSpec {
                 }
 
                 // RTN10b
-                pending("should not update when a message is sent but increments by one when ACK is received") {
+                it("should not update when a message is sent but increments by one when ACK is received") {
                     let client = ARTRealtime(options: AblyTests.commonAppSetup())
                     defer {
                         client.dispose()
@@ -960,7 +960,11 @@ class RealtimeClientConnection: QuickSpec {
                     }
                     let channel = client.channels.get("test")
 
-                    for index in 0...5 {
+                    expect(client.connection.serial).to(equal(-1))
+                    expect(client.connection.state).toEventually(equal(ARTRealtimeConnectionState.Connected), timeout: testTimeout)
+                    expect(client.connection.serial).to(equal(-1))
+
+                    for index in 0...3 {
                         waitUntil(timeout: testTimeout) { done in
                             channel.publish(nil, data: "message", cb: { errorInfo in
                                 expect(errorInfo).to(beNil())