diff -r bf840a3d1af2 -r be9c4131a8f4 mercurial/patch.py
--- a/mercurial/patch.py	Thu Sep 02 11:20:23 2010 +0200
+++ b/mercurial/patch.py	Thu Sep 02 12:08:13 2010 +0200
@@ -1352,7 +1352,7 @@
     '''print base85-encoded binary diff'''
     def gitindex(text):
         if not text:
-            return '0' * 40
+            return hex(nullid)
         l = len(text)
         s = util.sha1('blob %d\0' % l)
         s.update(text)