--- a/hgext3rd/topic/discovery.py	Tue Jul 31 13:06:20 2018 +0200
+++ b/hgext3rd/topic/discovery.py	Tue Jul 31 07:38:37 2018 -0500
@@ -16,7 +16,7 @@
 try:
     from mercurial import wireproto
     wireproto.branchmap
-except ImportError: # <= hg-4.5
+except (AttributeError, ImportError): # <= hg-4.5
     from mercurial import wireprotov1server as wireproto
 
 def _headssummary(orig, pushop, *args, **kwargs):