diff --git a/src/Event.php b/src/Event.php
index d78442f..1154164 100644
--- a/src/Event.php
+++ b/src/Event.php
@@ -93,7 +93,7 @@ public static function connectionEstablished(Event $event): bool
         return $event->getEvent() === 'pusher:connection_established';
     }
 
-    public static function subscribeOn(string $channel, string $authKey = null): array
+    public static function subscribeOn(string $channel, string $authKey = null, string $channelData = null): array
     {
         $data = ['channel' => $channel];
 
@@ -101,6 +101,10 @@ public static function subscribeOn(string $channel, string $authKey = null): arr
             $data['auth'] = $authKey;
         }
 
+        if ($channelData) {
+            $data['channel_data'] = $channelData;
+        }
+
         return ['event' => 'pusher:subscribe', 'data' => $data];
     }