diff -r 839c2879edcc -r 13313d0cab71 hgext3rd/topic/discovery.py
--- a/hgext3rd/topic/discovery.py	Thu Jun 22 09:47:14 2017 +0200
+++ b/hgext3rd/topic/discovery.py	Thu Jun 22 10:13:29 2017 +0200
@@ -4,7 +4,6 @@
 
 from mercurial.i18n import _
 from mercurial import (
-    branchmap,
     bundle2,
     discovery,
     error,
@@ -13,15 +12,15 @@
     wireproto,
 )
 
-from . import topicmap
-
 def _headssummary(orig, *args):
     # In mercurial < 4.2, we receive repo, remote and outgoing as arguments
     if len(args) == 3:
+        pushoparg = False
         repo, remote, outgoing = args
 
     # In mercurial > 4.3, we receive the pushop as arguments
     elif len(args) == 1:
+        pushoparg = True
         pushop = args[0]
         repo = pushop.repo.unfiltered()
         remote = pushop.remote
@@ -33,38 +32,44 @@
                   or bool(remote.listkeys('phases').get('publishing', False)))
     if publishing or not remote.capable('topics'):
         return orig(*args)
-    oldrepo = repo.__class__
-    oldbranchcache = branchmap.branchcache
-    oldfilename = branchmap._filename
-    try:
-        class repocls(repo.__class__):
-            def __getitem__(self, key):
-                ctx = super(repocls, self).__getitem__(key)
-                oldbranch = ctx.branch
+
+    class repocls(repo.__class__):
+        def __getitem__(self, key):
+            ctx = super(repocls, self).__getitem__(key)
+            oldbranch = ctx.branch
+
+            def branch():
+                branch = oldbranch()
+                topic = ctx.topic()
+                if topic:
+                    branch = "%s:%s" % (branch, topic)
+                return branch
 
-                def branch():
-                    branch = oldbranch()
-                    topic = ctx.topic()
-                    if topic:
-                        branch = "%s:%s" % (branch, topic)
-                    return branch
+            ctx.branch = branch
+            return ctx
 
-                ctx.branch = branch
-                return ctx
-
+    oldrepo = repo.__class__
+    try:
         repo.__class__ = repocls
-        branchmap.branchcache = topicmap.topiccache
-        branchmap._filename = topicmap._filename
-        summary = orig(*args)
+        unxx = repo.filtered('unfiltered-topic')
+        repo.unfiltered = lambda: unxx
+        if pushoparg:
+            try:
+                pushop.repo = repo
+                summary = orig(pushop)
+            finally:
+                pushop.repo = repo
+        else:
+            summary = orig(repo, remote, outgoing)
         for key, value in summary.iteritems():
             if ':' in key: # This is a topic
                 if value[0] is None and value[1]:
                     summary[key] = ([value[1].pop(0)], ) + value[1:]
         return summary
     finally:
+        if 'unfiltered' in vars(repo):
+            del repo.unfiltered
         repo.__class__ = oldrepo
-        branchmap.branchcache = oldbranchcache
-        branchmap._filename = oldfilename
 
 def wireprotobranchmap(orig, repo, proto):
     oldrepo = repo.__class__