diff --git a/mercurial/vfs.py b/mercurial/vfs.py
--- a/mercurial/vfs.py
+++ b/mercurial/vfs.py
@@ -649,7 +649,7 @@
         self._running = True
 
         for i in range(threadcount):
-            t = threading.Thread(target=self._worker, name=b'backgroundcloser')
+            t = threading.Thread(target=self._worker, name='backgroundcloser')
             self._threads.append(t)
             t.start()