diff -r db3e7f6b5ceb -r 92e3db149d7d hgext3rd/topic/discovery.py
--- a/hgext3rd/topic/discovery.py	Fri Jul 12 23:24:04 2019 -0700
+++ b/hgext3rd/topic/discovery.py	Sat Jul 13 00:17:03 2019 -0700
@@ -14,6 +14,7 @@
 )
 from . import (
     common,
+    compat,
 )
 
 try:
@@ -49,7 +50,7 @@
     def remotebranchmap():
         # drop topic information from changeset about to be published
         result = collections.defaultdict(list)
-        for branch, heads in origremotebranchmap().iteritems():
+        for branch, heads in compat.branchmapitems(origremotebranchmap()):
             if ':' not in branch:
                 result[branch].extend(heads)
             else: