diff -r 734515aca84d -r 8a73132214a3 mercurial/debugcommands.py
--- a/mercurial/debugcommands.py	Tue Apr 10 14:29:15 2018 -0700
+++ b/mercurial/debugcommands.py	Tue Apr 10 18:16:47 2018 -0700
@@ -83,6 +83,7 @@
     vfs as vfsmod,
     wireprotoframing,
     wireprotoserver,
+    wireprototypes,
 )
 from .utils import (
     dateutil,
@@ -2910,7 +2911,9 @@
 
         if opts['peer'] == 'http2':
             ui.write(_('creating http peer for wire protocol version 2\n'))
-            peer = httppeer.httpv2peer(ui, path, opener)
+            peer = httppeer.httpv2peer(
+                ui, path, 'api/%s' % wireprototypes.HTTPV2,
+                opener, httppeer.urlreq.request, {})
         elif opts['peer'] == 'raw':
             ui.write(_('using raw connection to peer\n'))
             peer = None