diff --git a/mercurial/wireproto.py b/mercurial/wireproto.py
--- a/mercurial/wireproto.py
+++ b/mercurial/wireproto.py
@@ -859,7 +859,8 @@
                     _('server has pull-based clones disabled'),
                     hint=_('remove --pull if specified or upgrade Mercurial'))
 
-        chunks = exchange.getbundlechunks(repo, 'serve', **opts)
+        chunks = exchange.getbundlechunks(repo, 'serve',
+                                          **pycompat.strkwargs(opts))
     except error.Abort as exc:
         # cleanly forward Abort error to the client
         if not exchange.bundle2requested(opts.get('bundlecaps')):