--- a/hgext/remotefilelog/fileserverclient.py	Sat Oct 13 05:09:18 2018 +0300
+++ b/hgext/remotefilelog/fileserverclient.py	Tue Nov 13 17:41:26 2018 +0300
@@ -18,6 +18,7 @@
 from mercurial.node import bin, hex, nullid
 from mercurial import (
     error,
+    pycompat,
     revlog,
     sshpeer,
     util,
@@ -119,7 +120,7 @@
         def _callstream(self, command, **opts):
             supertype = super(remotefilepeer, self)
             if not util.safehasattr(supertype, '_sendrequest'):
-                self._updatecallstreamopts(command, opts)
+                self._updatecallstreamopts(command, pycompat.byteskwargs(opts))
             return super(remotefilepeer, self)._callstream(command, **opts)
 
     peer.__class__ = remotefilepeer