diff --git a/mercurial/peer.py b/mercurial/peer.py
--- a/mercurial/peer.py
+++ b/mercurial/peer.py
@@ -10,6 +10,7 @@
 
 from . import (
     error,
+    pycompat,
     util,
 )
 
@@ -92,7 +93,8 @@
         if not encresref:
             return encargsorres # a local result in this case
         self = args[0]
-        encresref.set(self._submitone(f.__name__, encargsorres))
+        cmd = pycompat.bytesurl(f.__name__)  # ensure cmd is ascii bytestr
+        encresref.set(self._submitone(cmd, encargsorres))
         return next(batchable)
     setattr(plain, 'batchable', f)
     return plain