--- a/mercurial/revset.py	Mon Nov 22 17:57:11 2010 +0100
+++ b/mercurial/revset.py	Mon Nov 22 18:15:58 2010 +0100
@@ -715,7 +715,7 @@
 }
 
 def optimize(x, small):
-    if x == None:
+    if x is None:
         return 0, x
 
     smallbonus = 1