--- a/mercurial/dispatch.py	Fri Nov 05 15:13:22 2010 +0100
+++ b/mercurial/dispatch.py	Fri Nov 05 15:54:32 2010 -0400
@@ -453,7 +453,7 @@
     cmd = args[0]
     try:
         aliases, entry = cmdutil.findcmd(cmd, cmdtable, lui.config("ui", "strict"))
-    except error.UnknownCommand:
+    except (error.AmbiguousCommand, error.UnknownCommand):
         commands.norepo = norepo
         os.chdir(cwd)
         return