diff --git a/packages/realtime_client/lib/src/realtime_channel.dart b/packages/realtime_client/lib/src/realtime_channel.dart
index 42a2470c..3212eb2d 100644
--- a/packages/realtime_client/lib/src/realtime_channel.dart
+++ b/packages/realtime_client/lib/src/realtime_channel.dart
@@ -70,7 +70,7 @@ class RealtimeChannel {
       socket.remove(this);
     });
 
-    _onError((String? reason) {
+    _onError((reason) {
       if (isLeaving || isClosed) {
         return;
       }
@@ -260,9 +260,9 @@ class RealtimeChannel {
   }
 
   /// Registers a callback that will be executed when the channel encounteres an error.
-  void _onError(void Function(String?) callback) {
+  void _onError(Function callback) {
     onEvents(ChannelEvents.error.eventName(), ChannelFilter(),
-        (reason, [ref]) => callback(reason?.toString()));
+        (reason, [ref]) => callback(reason));
   }
 
   /// Sets up a listener on your Supabase database.
diff --git a/packages/realtime_client/lib/src/realtime_client.dart b/packages/realtime_client/lib/src/realtime_client.dart
index 5529029e..de4ea76c 100644
--- a/packages/realtime_client/lib/src/realtime_client.dart
+++ b/packages/realtime_client/lib/src/realtime_client.dart
@@ -48,7 +48,7 @@ class RealtimeCloseEvent {
 
   @override
   String toString() {
-    return 'RealtimeCloseEvent{code: $code, reason: $reason}';
+    return 'RealtimeCloseEvent(code: $code, reason: $reason)';
   }
 }
 
diff --git a/packages/realtime_client/test/mock_test.dart b/packages/realtime_client/test/mock_test.dart
index ccd77089..81b3b64f 100644
--- a/packages/realtime_client/test/mock_test.dart
+++ b/packages/realtime_client/test/mock_test.dart
@@ -268,7 +268,9 @@ void main() {
       final subscribeCallback =
           expectAsync2((RealtimeSubscribeStatus event, error) {
         if (event == RealtimeSubscribeStatus.channelError) {
-          expect(error, isNull);
+          expect(error, isA<RealtimeCloseEvent>());
+          error as RealtimeCloseEvent;
+          expect(error.reason, "heartbeat timeout");
         } else {
           expect(event, RealtimeSubscribeStatus.closed);
         }
@@ -285,6 +287,7 @@ void main() {
 
       channel.subscribe(subscribeCallback);
 
+      await Future.delayed(Duration(milliseconds: 200));
       await client.conn!.sink
           .close(Constants.wsCloseNormal, "heartbeat timeout");
     });
diff --git a/packages/realtime_client/test/socket_test.dart b/packages/realtime_client/test/socket_test.dart
index 8a61d0c9..84f9eb2f 100644
--- a/packages/realtime_client/test/socket_test.dart
+++ b/packages/realtime_client/test/socket_test.dart
@@ -171,6 +171,7 @@ void main() {
       });
 
       socket.connect();
+      await Future.delayed(const Duration(milliseconds: 200));
       expect(opens, 1);
 
       socket.sendHeartbeat();
@@ -229,7 +230,7 @@ void main() {
       expect(closes, 1);
     });
 
-    test('calls connection close callback', () {
+    test('calls connection close callback', () async {
       final mockedSocketChannel = MockIOWebSocketChannel();
       final mockedSocket = RealtimeClient(
         socketEndpoint,
@@ -247,7 +248,10 @@ void main() {
       const tReason = 'reason';
 
       mockedSocket.connect();
+      mockedSocket.connState = SocketStates.open;
+      await Future.delayed(const Duration(milliseconds: 200));
       mockedSocket.disconnect(code: tCode, reason: tReason);
+      await Future.delayed(const Duration(milliseconds: 200));
 
       verify(
         () => mockedSink.close(