--- a/mercurial/merge.py	Sat Oct 28 23:37:59 2006 -0300
+++ b/mercurial/merge.py	Sun Oct 29 10:53:51 2006 +0100
@@ -34,7 +34,7 @@
 
     fca = fcm.ancestor(fco)
     if not fca:
-        fca = repo.filectx(fw, fileid=-1)
+        fca = repo.filectx(fw, fileid=nullrev)
     a = repo.wjoin(fw)
     b = temp("base", fca)
     c = temp("other", fco)