diff -r 3439b66f506e -r e03ece039b3a mercurial/revset.py
--- a/mercurial/revset.py	Fri Oct 03 00:30:58 2014 -0500
+++ b/mercurial/revset.py	Fri Oct 03 00:31:18 2014 -0500
@@ -2919,11 +2919,6 @@
             return True
         return False
 
-    def __sub__(self, x):
-        filterfunc = x.__contains__
-        return orderedlazyset(self, lambda r: not filterfunc(r),
-                              ascending=self.isascending())
-
     def __add__(self, x):
         kwargs = {}
         if self.isascending() and x.isascending():