diff -r d503d5a786f3 -r 18869fcfbc92 src/mercurialserver/servelog.py
--- a/src/mercurialserver/servelog.py	Fri Jul 20 17:17:49 2018 +0200
+++ b/src/mercurialserver/servelog.py	Wed Oct 31 13:21:37 2018 -0700
@@ -33,7 +33,7 @@
         op=op,
         key=ruleset.rules.get('user'),
         ssh_connection=os.environ['SSH_CONNECTION'],))
-    with open(repo.join("mercurial-server.log"), "a+") as log:
+    with open(repo.vfs.join("mercurial-server.log"), "a+") as log:
         fcntl.flock(log.fileno(), fcntl.LOCK_EX)
         log.seek(0, os.SEEK_END)
         # YAML log file format