diff -r 3a2367e6c6f2 -r 835ccc2a5ef1 mercurial/debugcommands.py
--- a/mercurial/debugcommands.py	Mon Apr 09 19:35:39 2018 -0700
+++ b/mercurial/debugcommands.py	Tue Apr 10 10:22:26 2018 -0700
@@ -2915,7 +2915,8 @@
             raise error.Abort(_('--peer %s not supported with HTTP peers') %
                               opts['peer'])
         else:
-            peer = httppeer.httppeer(ui, path, url, opener)
+            peer = httppeer.httppeer(ui, path, url, opener,
+                                     requestbuilder=httppeer.urlreq.request)
             peer._fetchcaps()
 
         # We /could/ populate stdin/stdout with sock.makefile()...