--- a/mercurial/wireprotov2server.py	Thu Aug 30 17:43:47 2018 -0700
+++ b/mercurial/wireprotov2server.py	Mon Sep 17 09:49:28 2018 -0700
@@ -20,6 +20,7 @@
     discovery,
     encoding,
     error,
+    narrowspec,
     pycompat,
     streamclone,
     util,
@@ -429,6 +430,7 @@
         'commands': {},
         'compression': compression,
         'framingmediatypes': [FRAMINGTYPE],
+        'pathfilterprefixes': set(narrowspec.VALID_PREFIXES),
     }
 
     # TODO expose available changesetdata fields.