diff -r 482443557cad -r affec9fb56ef mercurial/subrepo.py
--- a/mercurial/subrepo.py	Fri Sep 10 22:36:04 2010 +0200
+++ b/mercurial/subrepo.py	Fri Sep 10 22:52:00 2010 +0200
@@ -305,6 +305,9 @@
     def diff(self, diffopts, node2, match, prefix, **opts):
         try:
             node1 = node.bin(self._state[1])
+            # We currently expect node2 to come from substate and be
+            # in hex format
+            node2 = node.bin(node2)
             cmdutil.diffordiffstat(self._repo.ui, self._repo, diffopts,
                                    node1, node2, match,
                                    prefix=os.path.join(prefix, self._path),