diff --git a/mercurial/manifest.py b/mercurial/manifest.py
index b5e5ddf48bd2650efe06d31551214498c0d5d572_bWVyY3VyaWFsL21hbmlmZXN0LnB5..14ad8e2a4abef1ede952f195d2fddf7b16a01db9_bWVyY3VyaWFsL21hbmlmZXN0LnB5 100644
--- a/mercurial/manifest.py
+++ b/mercurial/manifest.py
@@ -927,7 +927,8 @@
         else:
             self._dirlogcache = {'': self}
 
-        super(manifestrevlog, self).__init__(opener, indexfile)
+        super(manifestrevlog, self).__init__(opener, indexfile,
+                                             checkambig=bool(dir))
 
     @property
     def fulltextcache(self):