--- a/mercurial/commands.py	Wed May 18 23:48:17 2011 +0200
+++ b/mercurial/commands.py	Wed May 18 17:05:30 2011 -0500
@@ -1865,7 +1865,9 @@
         ts = 0
         heads = set()
         for rev in xrange(numrevs):
-            dbase = r.base(rev)
+            dbase = r.deltaparent(rev)
+            if dbase == -1:
+                dbase = rev
             cbase = r.chainbase(rev)
             p1, p2 = r.parentrevs(rev)
             rs = r.rawsize(rev)