diff -r 296b09dcef63 -r d716b1cec5cf mercurial/revset.py
--- a/mercurial/revset.py	Fri Nov 14 09:33:28 2014 -0800
+++ b/mercurial/revset.py	Fri Nov 14 16:38:58 2014 -0800
@@ -10,7 +10,6 @@
 import node
 import heapq
 import match as matchmod
-import ancestor as ancestormod
 from i18n import _
 import encoding
 import obsolete as obsmod
@@ -406,7 +405,7 @@
     else:
         exclude = getset(repo, spanset(repo), args[1])
 
-    results = set(ancestormod.missingancestors(include, exclude, cl.parentrevs))
+    results = set(cl.findmissingrevs(common=exclude, heads=include))
     return subset & results
 
 def bisect(repo, subset, x):