diff --git a/src/notify.py b/src/notify.py
index c66826925..d0b26cadc 100644
--- a/src/notify.py
+++ b/src/notify.py
@@ -91,7 +91,7 @@ class NotificationResponseManager:
 			# on a popup before the program finishes registering this callback
 			gobject.timeout_add(1000, self.on_action_invoked, id, reason)
 
-	def on_closed(self, id, reason):
+	def on_closed(self, id, reason = None):
 		if self.pending.has_key(id):
 			del self.pending[id]