--- a/mercurial/commands.py	Tue Nov 18 12:29:30 2014 -0600
+++ b/mercurial/commands.py	Tue Nov 18 16:14:32 2014 -0800
@@ -6185,7 +6185,6 @@
             raise util.Abort(_("uncommitted changes"))
         if rev is None:
             rev = repo[repo[None].branch()].rev()
-        mergemod.checkunknown(repo, repo[None], repo[rev])
 
     repo.ui.setconfig('ui', 'forcemerge', tool, 'update')