diff --git a/Spec/RealtimeClient.swift b/Spec/RealtimeClient.swift
index 63e66cf5e..50e742bfe 100644
--- a/Spec/RealtimeClient.swift
+++ b/Spec/RealtimeClient.swift
@@ -1328,54 +1328,29 @@ class RealtimeClient: QuickSpec {
                 expect(result).to(equal(expectedOrder))
             }
 
-            // Possible issue of https://github.com/ably/ably-ios/issues/640
-            xit("should unlock queue when the timer ends") {
-                let options = ARTClientOptions(key: "xxxx:xxxx")
-                options.autoConnect = false
-                let client = ARTRealtime(options: options)
-                let channel = client.channels.get("foo")
-
-                waitUntil(timeout: testTimeout) { done in
-                    // Schedule a timer in the `internalDispatchQueue`
-                    let listener = client.internalEventEmitter.once { _ in }
-                    listener.setTimer(0.2, onTimeout: {
-                        // another lock
-                        channel.unsubscribe()
-                        done()
-                    })
-                    listener.startTimer()
-
-                    // lock
-                    channel.unsubscribe()
-                }
-            }
-
             class AblyManager {
                 static let sharedClient = ARTRealtime(options: { $0.autoConnect = false; return $0 }(ARTClientOptions(key: "xxxx:xxxx")))
             }
 
-            // Possible issue of https://github.com/ably/ably-ios/issues/640
-            xit("should dispatch in user queue") {
+            // Issue https://github.com/ably/ably-ios/issues/640
+            it("should dispatch in user queue when removing an observer") {
                 class Foo {
-                    let channel = "foo"
                     init() {
-                        AblyManager.sharedClient.channels.get(channel).subscribe { _ in
+                        AblyManager.sharedClient.channels.get("foo").subscribe { _ in
                             // keep reference
                             self.update()
                         }
                     }
-                    deinit {
-                        close()
-                    }
                     func update() {
                     }
-                    func close() {
-                        AblyManager.sharedClient.channels.get(channel).unsubscribe()
+                    deinit {
+                        AblyManager.sharedClient.channels.get("foo").unsubscribe()
                     }
                 }
 
-                let foo = Foo()
-                foo.close()
+                var foo: Foo? = Foo()
+                foo = nil
+                AblyManager.sharedClient.channels.get("foo").unsubscribe()
             }
 
             it("should never register any connection listeners for internal use with the public EventEmitter") {