diff -r 83d965803325 -r 6b5ca1d0aa1e mercurial/debugcommands.py
--- a/mercurial/debugcommands.py	Sun Jul 15 18:22:40 2018 +0900
+++ b/mercurial/debugcommands.py	Sun Jul 15 18:24:57 2018 +0900
@@ -1619,7 +1619,7 @@
         if opts['rev']:
             raise error.Abort('cannot select revision when creating marker')
         metadata = {}
-        metadata['user'] = opts['user'] or ui.username()
+        metadata['user'] = encoding.fromlocal(opts['user'] or ui.username())
         succs = tuple(parsenodeid(succ) for succ in successors)
         l = repo.lock()
         try: