--- a/mercurial/localrepo.py	Fri Sep 27 00:11:03 2019 +0200
+++ b/mercurial/localrepo.py	Fri Sep 27 06:24:42 2019 +0200
@@ -748,6 +748,8 @@
     # meaningful on such old repos.
     if b'revlogv1' in requirements or REVLOGV2_REQUIREMENT in requirements:
         options.update(resolverevlogstorevfsoptions(ui, requirements, features))
+    else: # explicitly mark repo as using revlogv0
+        options['revlogv0'] = True
 
     return options