diff -r ca430fb6a668 -r 751135cca13c mercurial/subrepo.py
--- a/mercurial/subrepo.py	Thu Jan 31 19:13:13 2013 +0100
+++ b/mercurial/subrepo.py	Thu Jan 31 01:44:29 2013 +0100
@@ -423,6 +423,7 @@
             v = r.ui.config(s, k)
             if v:
                 self._repo.ui.setconfig(s, k, v)
+        self._repo.ui.setconfig('ui', '_usedassubrepo', 'True')
         self._initrepo(r, state[0], create)
 
     @annotatesubrepoerror