--- a/mercurial/revset.py	Mon Oct 06 23:37:39 2014 -0700
+++ b/mercurial/revset.py	Mon Oct 06 23:45:07 2014 -0700
@@ -271,7 +271,7 @@
 
     if not m or not n:
         return baseset()
-    m, n = m[0], n[-1]
+    m, n = m.first(), n.last()
 
     if m < n:
         r = spanset(repo, m, n + 1)