diff -r 9fd4f7af42ea -r 95054317e172 mercurial/localrepo.py
--- a/mercurial/localrepo.py	Wed Jan 27 15:06:02 2021 +0100
+++ b/mercurial/localrepo.py	Thu Jan 28 15:12:48 2021 +0100
@@ -3639,11 +3639,11 @@
         # effectively locks out old clients and prevents them from
         # mucking with a repo in an unknown format.
         #
-        # The revlog header has version 2, which won't be recognized by
+        # The revlog header has version 65535, which won't be recognized by
         # such old clients.
         hgvfs.append(
             b'00changelog.i',
-            b'\0\0\0\2 dummy changelog to prevent using the old repo '
+            b'\0\0\xFF\xFF dummy changelog to prevent using the old repo '
             b'layout',
         )