--- a/hgext/mozext/__init__.py
+++ b/hgext/mozext/__init__.py
@@ -1391,17 +1391,17 @@ def reposetup(ui, repo):
         def remoterefs(self):
             return remoterefs(self)
 
         @util.propertycache
         def changetracker(self):
             if ui.configbool('mozext', 'disable_local_database'):
                 return None
             try:
-                return ChangeTracker(self.join('changetracker.db'))
+                return ChangeTracker(self.vfs.join('changetracker.db'))
             except Exception as e:
                 raise util.Abort(e.message)
 
         def _update_remote_refs(self, remote, tree):
             existing_refs = set()
             incoming_refs = set()
 
             for ref in self.remoterefs:

--- a/hgext/overlay/__init__.py
+++ b/hgext/overlay/__init__.py
@@ -264,17 +264,17 @@ def _dooverlay(sourcerepo, sourceurl, so
 def _mirrorrepo(ui, repo, url):
     """Mirror a source repository into the .hg directory of another."""
     u = util.url(url)
     if u.islocal():
         raise error.Abort(_('source repo cannot be local'))
 
     # Remove scheme from path and normalize reserved characters.
     path = url.replace('%s://' % u.scheme, '').replace('/', '_')
-    mirrorpath = repo.join(store.encodefilename(path))
+    mirrorpath = repo.vfs.join(store.encodefilename(path))
 
     peer = hg.peer(ui, {}, url)
     mirrorrepo = hg.repository(ui, mirrorpath,
                                create=not os.path.exists(mirrorpath))
 
     missingheads = [head for head in peer.heads() if head not in mirrorrepo]
     if missingheads:
         ui.write(_('pulling %s into %s\n' % (url, mirrorpath)))