--- a/mercurial/filelog.py	Mon May 03 12:22:06 2021 +0200
+++ b/mercurial/filelog.py	Mon May 03 12:22:16 2021 +0200
@@ -71,7 +71,7 @@
 
     def lookup(self, node):
         return storageutil.fileidlookup(
-            self._revlog, node, self._revlog.indexfile
+            self._revlog, node, self._revlog._indexfile
         )
 
     def linkrev(self, rev):