--- a/hgext3rd/topic/stack.py	Wed Jun 28 02:45:57 2017 +0200
+++ b/hgext3rd/topic/stack.py	Wed Jun 28 01:53:21 2017 +0200
@@ -55,24 +55,33 @@
         label = 'topic.active'
 
     data = stackdata(repo, branch=branch, topic=topic)
-    fm.plain(_('### topic: %s') % ui.label(topic, label),
-             label='topic.stack.summary.topic')
+    if topic is not None:
+        fm.plain(_('### topic: %s')
+                 % ui.label(topic, label),
+                 label='topic.stack.summary.topic')
 
-    if 1 < data['headcount']:
-        fm.plain(' (')
-        fm.plain('%d heads' % data['headcount'],
-                 label='topic.stack.summary.headcount.multiple')
-        fm.plain(')')
-    fm.plain('\n')
+        if 1 < data['headcount']:
+            fm.plain(' (')
+            fm.plain('%d heads' % data['headcount'],
+                     label='topic.stack.summary.headcount.multiple')
+            fm.plain(')')
+        fm.plain('\n')
     fm.plain(_('### branch: %s')
              % '+'.join(data['branches']), # XXX handle multi branches
              label='topic.stack.summary.branches')
-    if data['behindcount'] == -1:
-        fm.plain(', ')
-        fm.plain('ambigious rebase destination', label='topic.stack.summary.behinderror')
-    elif data['behindcount']:
-        fm.plain(', ')
-        fm.plain('%d behind' % data['behindcount'], label='topic.stack.summary.behindcount')
+    if topic is None:
+        if 1 < data['headcount']:
+            fm.plain(' (')
+            fm.plain('%d heads' % data['headcount'],
+                     label='topic.stack.summary.headcount.multiple')
+            fm.plain(')')
+    else:
+        if data['behindcount'] == -1:
+            fm.plain(', ')
+            fm.plain('ambigious rebase destination', label='topic.stack.summary.behinderror')
+        elif data['behindcount']:
+            fm.plain(', ')
+            fm.plain('%d behind' % data['behindcount'], label='topic.stack.summary.behindcount')
     fm.plain('\n')
 
     for idx, r in enumerate(getstack(repo, branch=branch, topic=topic), 1):

--- a/tests/test-stack-branch.t	Wed Jun 28 02:45:57 2017 +0200
+++ b/tests/test-stack-branch.t	Wed Jun 28 01:53:21 2017 +0200
@@ -55,7 +55,6 @@
   $ hg up other
   0 files updated, 0 files merged, 4 files removed, 0 files unresolved
   $ hg stack
-  ### topic: None
   ### branch: other
   b2@ c_b (current)
   b1: c_a
@@ -71,7 +70,6 @@
   $ hg branch
   foo
   $ hg stack
-  ### topic: None
   ### branch: foo
   b4@ c_f (current)
   b3: c_e
@@ -120,7 +118,6 @@
   o  0 other {} public c_a
   
   $ hg stack
-  ### topic: None
   ### branch: foo
   b4$ c_f (unstable)
   b3$ c_e (unstable)
@@ -130,7 +127,6 @@
   $ hg up b3
   2 files updated, 0 files merged, 0 files removed, 0 files unresolved
   $ hg stack
-  ### topic: None
   ### branch: foo
   b4$ c_f (unstable)
   b3$ c_e (current unstable)
@@ -200,8 +196,7 @@
 Test output
 
   $ hg stack
-  ### topic: None (2 heads)
-  ### branch: foo
+  ### branch: foo (2 heads)
   b6: c_f
   b5: c_e
   b2^ c_d (base)
@@ -244,8 +239,7 @@
   
 
   $ hg stack
-  ### topic: None (2 heads)
-  ### branch: foo
+  ### branch: foo (2 heads)
   b6$ c_f (unstable)
   b5$ c_e (unstable)
   b2^ c_D (base)

--- a/tests/test-topic-stack.t	Wed Jun 28 02:45:57 2017 +0200
+++ b/tests/test-topic-stack.t	Wed Jun 28 01:53:21 2017 +0200
@@ -129,7 +129,6 @@
 
   $ hg topic --clear
   $ hg stack
-  ### topic: None
   ### branch: default
   b6@ c_f (current)
   b5: c_e