--- a/mercurial/context.py	Tue Jul 27 23:40:46 2010 +0900
+++ b/mercurial/context.py	Thu Jul 29 10:39:59 2010 +0900
@@ -940,7 +940,9 @@
 
         returns True if different than fctx.
         """
-        return self._repo.wread(self._path) != fctx.data()
+        # fctx should be a filectx (not a wfctx)
+        # invert comparison to reuse the same code path
+        return fctx.cmp(self)
 
 class memctx(object):
     """Use memctx to perform in-memory commits via localrepo.commitctx().