diff --git a/tools/cluster-merge b/tools/cluster-merge
index 89eb563e4ff960dc23fa488fa4482b9228436de2..d006869ad2332d0fa2008552ff716a7d31b15270 100755
--- a/tools/cluster-merge
+++ b/tools/cluster-merge
@@ -386,7 +386,7 @@ class Merger(object):
       logging.info("Merging config")
       self._FetchRemoteConfig()
 
-      def _OfflineClusterMerge():
+      def _OfflineClusterMerge(_):
         """Closure run when master daemons stopped
 
         """