diff -r ebdc2a6a9a25 -r 137f8b04901e hgext3rd/topic/__init__.py
--- a/hgext3rd/topic/__init__.py	Sun Aug 14 20:40:46 2016 +0200
+++ b/hgext3rd/topic/__init__.py	Fri Aug 12 23:59:37 2016 +0200
@@ -289,6 +289,13 @@
             fm.plain(' %s ' % marker, label=label)
         fm.write('topic', '%s', topic, label=label)
         fm.data(active=active)
+        if ui.verbose:
+            # XXX we should include the data even when not verbose
+            data = stack.stackdata(repo, topic)
+            fm.plain('\t(')
+            fm.write('changesetcount', '%d changesets', data['changesetcount'],
+                     label='topic.list.changesetcount')
+            fm.plain(')')
         fm.plain('\n')
     fm.end()