diff --git a/Source/Bot.py b/Source/Bot.py
index 554f192..7645e71 100644
--- a/Source/Bot.py
+++ b/Source/Bot.py
@@ -45,7 +45,7 @@ def __init__(self, bot_name, commands, room_ids, background_tasks=[], host='stac
         self._startup_message = self.name + " starting..."
         self._standby_message = "Switching to standby mode."
         self._failover_message = "Failover received."
-        self._on_event_callback = lambda: None
+        self._on_event_callback = lambda event: None
 
         background_tasks.append(BackgroundTask(self._command_manager.cleanup_finished_commands, interval=3))
         self._background_task_manager = BackgroundTaskManager(background_tasks)