diff -r 8afaf7cef35a -r da05fe01170b mercurial/revset.py
--- a/mercurial/revset.py	Wed Sep 17 00:28:37 2014 +0900
+++ b/mercurial/revset.py	Fri Sep 12 16:21:13 2014 -0700
@@ -666,10 +666,8 @@
     # Both sets need to be ascending in order to lazily return the union
     # in the correct order.
     args.ascending()
-
-    subsetset = subset.set()
-    result = (orderedlazyset(s, subsetset.__contains__, ascending=True) +
-              orderedlazyset(args, subsetset.__contains__, ascending=True))
+    result = (orderedlazyset(s, subset.__contains__, ascending=True) +
+              orderedlazyset(args, subset.__contains__, ascending=True))
 
     # Wrap result in a lazyset since it's an _addset, which doesn't implement
     # all the necessary functions to be consumed by callers.