diff -r ac3a68cb16eb -r bd70f645cfb0 mercurial/patch.py
--- a/mercurial/patch.py	Sat Oct 31 18:00:05 2009 +0100
+++ b/mercurial/patch.py	Sat Oct 31 18:01:08 2009 +0100
@@ -480,6 +480,8 @@
         self.hunk = [ desc ]
         self.a = []
         self.b = []
+        self.starta = self.lena = None
+        self.startb = self.lenb = None
         if context:
             self.read_context_hunk(lr)
         else: