--- a/mercurial/revset.py	Thu Nov 27 02:04:30 2014 +0100
+++ b/mercurial/revset.py	Tue Jan 06 11:23:38 2015 -0800
@@ -837,8 +837,9 @@
                 if lowesthead is None:
                     lowesthead = {}
                     for h in repo.heads():
-                        fnode = repo[h].manifest()[f]
-                        lowesthead[fl.rev(fnode)] = h
+                        fnode = repo[h].manifest().get(f)
+                        if fnode is not None:
+                            lowesthead[fl.rev(fnode)] = h
                 headrev = lowesthead.get(fr)
                 if headrev is None:
                     # content is nowhere unfiltered