diff -r 4335a75f0bd0 -r a3202fa83aff mercurial/filelog.py
--- a/mercurial/filelog.py	Thu Apr 05 15:09:41 2018 -0700
+++ b/mercurial/filelog.py	Thu Apr 05 15:18:23 2018 -0700
@@ -10,9 +10,13 @@
 import re
 import struct
 
+from .thirdparty.zope import (
+    interface as zi,
+)
 from . import (
     error,
     mdiff,
+    repository,
     revlog,
 )
 
@@ -39,6 +43,7 @@
     m, offs = parsemeta(text)
     return m and "censored" in m
 
+@zi.implementer(repository.ifilestorage)
 class filelog(revlog.revlog):
     def __init__(self, opener, path):
         super(filelog, self).__init__(opener,