diff -r c152e538b85b -r 6a1a4c212d50 mercurial/revset.py
--- a/mercurial/revset.py	Tue Mar 11 16:52:15 2014 -0700
+++ b/mercurial/revset.py	Thu Mar 13 13:47:21 2014 -0700
@@ -940,7 +940,7 @@
     hs = set()
     for b, ls in repo.branchmap().iteritems():
         hs.update(repo[h].rev() for h in ls)
-    return subset.filter(lambda r: r in hs)
+    return baseset(hs).filter(subset.__contains__)
 
 def heads(repo, subset, x):
     """``heads(set)``