--- a/mercurial/filelog.py	Mon Mar 15 19:55:52 2010 +0100
+++ b/mercurial/filelog.py	Tue Mar 16 01:12:46 2010 +0100
@@ -61,7 +61,7 @@
         """compare text with a given file revision"""
 
         # for renames, we have to go the slow way
-        if self.renamed(node):
+        if text.startswith('\1\n') or self.renamed(node):
             t2 = self.read(node)
             return t2 != text