--- a/mercurial/revset.py	Tue Jul 03 18:02:07 2012 +0200
+++ b/mercurial/revset.py	Wed Jul 04 09:38:07 2012 -0700
@@ -1151,6 +1151,8 @@
     Reverse order of set.
     """
     l = getset(repo, subset, x)
+    if not isinstance(l, list):
+        l = list(l)
     l.reverse()
     return l