--- a/mercurial/revlog.py	Sun Mar 26 16:31:01 2017 +0900
+++ b/mercurial/revlog.py	Sun Mar 26 17:12:06 2017 +0900
@@ -1488,7 +1488,7 @@
             # The revlog compressor added the header in the returned data.
             return '', compressed
 
-        if data[0] == '\0':
+        if data[0:1] == '\0':
             return '', data
         return 'u', data