diff --git a/services/real-time/app/coffee/Router.coffee b/services/real-time/app/coffee/Router.coffee
index 21d9e34b7d..17107e443a 100644
--- a/services/real-time/app/coffee/Router.coffee
+++ b/services/real-time/app/coffee/Router.coffee
@@ -100,7 +100,7 @@ module.exports = Router =
 					# Called with 4 args, things are as expected
 				else
 					logger.error { arguments: arguments }, "unexpected arguments"
-					return # ????
+					return callback?(new Error("unexpected arguments"))
 
 				WebsocketController.joinDoc client, doc_id, fromVersion, options, (err, args...) ->
 					if err?