mercurial/patch.py

--- a/mercurial/patch.py	Mon Apr 04 16:21:57 2011 -0500
+++ b/mercurial/patch.py	Mon Apr 04 16:21:59 2011 -0500
@@ -1324,7 +1324,7 @@
         opts = mdiff.defaultopts
 
     if not node1 and not node2:
-        node1 = repo.dirstate.parents()[0]
+        node1 = repo.dirstate.p1()
 
     def lrugetfilectx():
         cache = {}