--- a/contrib/perf.py	Fri Jul 20 11:17:33 2018 -0700
+++ b/contrib/perf.py	Fri Jul 20 11:37:31 2018 -0700
@@ -923,7 +923,7 @@
     """
     timer, fm = gettimer(ui, opts)
     def moonwalk():
-        for i in xrange(len(repo), -1, -1):
+        for i in repo.changelog.revs(start=(len(repo) - 1), stop=-1):
             ctx = repo[i]
             ctx.branch() # read changelog data (in addition to the index)
     timer(moonwalk)