diff -r 76b0b0fed2e3 -r 1ff35d76421c mercurial/merge.py
--- a/mercurial/merge.py	Wed Mar 25 13:55:32 2015 +0900
+++ b/mercurial/merge.py	Wed Mar 25 13:55:35 2015 +0900
@@ -1045,9 +1045,7 @@
                 raise util.Abort(_("uncommitted changes"),
                                  hint=_("use 'hg status' to list changes"))
             for s in sorted(wc.substate):
-                if wc.sub(s).dirty():
-                    raise util.Abort(_("uncommitted changes in "
-                                       "subrepository '%s'") % s)
+                wc.sub(s).bailifchanged()
 
         elif not overwrite:
             if p1 == p2: # no-op update