diff -r 774b4ea6ca58 -r cb8ae3cb0bbc hgext3rd/topic/__init__.py
--- a/hgext3rd/topic/__init__.py	Mon Oct 09 19:39:13 2017 +0530
+++ b/hgext3rd/topic/__init__.py	Tue Oct 10 22:40:41 2017 +0200
@@ -139,6 +139,7 @@
              }
 
 __version__ = '0.4.0.dev'
+
 testedwith = '4.0.2 4.1.3 4.2.3 4.3.3'
 minimumhgversion = '4.0'
 buglink = 'https://bz.mercurial-scm.org/'
@@ -338,14 +339,14 @@
             ct = self.currenttopic
             if not ct:
                 return tr
-            ctwasempty = stack.stackdata(self, topic=ct)['changesetcount'] == 0
+            ctwasempty = stack.stack(self, topic=ct).changesetcount == 0
 
             reporef = weakref.ref(self)
 
             def currenttopicempty(tr):
                 # check active topic emptyness
                 repo = reporef()
-                csetcount = stack.stackdata(repo, topic=ct)['changesetcount']
+                csetcount = stack.stack(repo, topic=ct).changesetcount
                 empty = csetcount == 0
                 if empty and not ctwasempty:
                     ui.status('active topic %r is now empty\n' % ct)
@@ -496,7 +497,7 @@
 
     ct = repo.currenttopic
     if clear:
-        empty = stack.stackdata(repo, topic=ct)['changesetcount'] == 0
+        empty = stack.stack(repo, topic=ct).changesetcount == 0
         if empty:
             if ct:
                 ui.status(_('clearing empty topic "%s"\n') % ct)
@@ -994,7 +995,7 @@
         # rebased commit. We have explicitly stored in config if rebase is
         # running.
         ot = repo.currenttopic
-        empty = stack.stackdata(repo, topic=ot)['changesetcount'] == 0
+        empty = stack.stack(repo, topic=ot).changesetcount == 0
         if repo.ui.hasconfig('experimental', 'topicrebase'):
             isrebase = True
         if repo.ui.configbool('_internal', 'keep-topic'):