diff --git a/mercurial/debugcommands.py b/mercurial/debugcommands.py
--- a/mercurial/debugcommands.py
+++ b/mercurial/debugcommands.py
@@ -1400,7 +1400,7 @@
             try:
                 st = vfs.lstat(name)
                 age = now - st[stat.ST_MTIME]
-                user = util.username(st.st_uid)
+                user = pycompat.fsencode(util.username(st.st_uid))
                 locker = vfs.readlock(name)
                 if ":" in locker:
                     host, pid = locker.split(':')