--- a/mercurial/commands.py	Sat Sep 29 13:41:02 2012 +0200
+++ b/mercurial/commands.py	Mon Oct 01 03:19:23 2012 +0200
@@ -833,7 +833,7 @@
             raise util.Abort(
                 _("a bookmark cannot have the name of an existing branch"))
         if rev:
-            marks[mark] = repo.lookup(rev)
+            marks[mark] = scmutil.revsingle(repo, rev).node()
         else:
             marks[mark] = cur
         if not inactive and cur == marks[mark]: