--- a/mercurial/commands.py	Wed Nov 12 14:47:48 2014 +0000
+++ b/mercurial/commands.py	Thu Nov 13 23:12:15 2014 -0800
@@ -6184,7 +6184,7 @@
             raise util.Abort(_("uncommitted changes"))
         if rev is None:
             rev = repo[repo[None].branch()].rev()
-        mergemod._checkunknown(repo, repo[None], repo[rev])
+        mergemod.checkunknown(repo, repo[None], repo[rev])
 
     repo.ui.setconfig('ui', 'forcemerge', tool, 'update')