diff --git a/src/Illuminate/Broadcasting/Broadcasters/AblyBroadcaster.php b/src/Illuminate/Broadcasting/Broadcasters/AblyBroadcaster.php
index <HASH>..<HASH> 100644
--- a/src/Illuminate/Broadcasting/Broadcasters/AblyBroadcaster.php
+++ b/src/Illuminate/Broadcasting/Broadcasters/AblyBroadcaster.php
@@ -76,7 +76,7 @@ class AblyBroadcaster extends Broadcaster
             $request->channel_name,
             $request->socket_id,
             $userData = array_filter([
-                'user_id' => $this->retrieveUser($request, $channelName)->getAuthIdentifier(),
+                'user_id' => (string) $this->retrieveUser($request, $channelName)->getAuthIdentifier(),
                 'user_info' => $result,
             ])
         );
Ably expects clientId as string (#<I>)

Ably uses the Pusher 'user_id' and maps it to 'clientId' which should be a string