--- a/mercurial/commands.py	Fri Sep 08 01:07:21 2006 +0200
+++ b/mercurial/commands.py	Fri Sep 08 02:16:16 2006 +0200
@@ -1940,7 +1940,7 @@
     revision to merge with must be provided.
     """
 
-    if node:
+    if node or branch:
         node = _lookup(repo, node, branch)
     else:
         heads = repo.heads()