diff -r 553e8f5aba7a -r 0c18aed2fcca mercurial/discovery.py
--- a/mercurial/discovery.py	Fri Jun 08 07:59:37 2012 -0700
+++ b/mercurial/discovery.py	Fri Jun 08 08:39:44 2012 -0700
@@ -214,8 +214,8 @@
                 if latest not in newheads:
                     continue
                 minhrev = min(cl.rev(h) for h in newheads)
-                reachable = cl.reachable(latest, cl.node(minhrev))
-                reachable.remove(latest)
+                reachable = [cl.node(rev) for rev in
+                             cl.ancestors([cl.rev(latest)], minhrev)]
                 newheads.difference_update(reachable)
         branches = set([None])
         newmap = {None: newheads}