--- a/hgext3rd/topic/stack.py	Fri Sep 15 22:48:55 2017 +0530
+++ b/hgext3rd/topic/stack.py	Fri Sep 15 23:13:05 2017 +0530
@@ -207,6 +207,9 @@
         label = 'topic.active'
 
     data = stackdata(repo, branch=branch, topic=topic)
+    empty = False
+    if data['changesetcount'] == 0:
+        empty = True
     if topic is not None:
         fm.plain(_('### topic: %s')
                  % ui.label(topic, label),
@@ -236,6 +239,9 @@
             fm.plain('%d behind' % data['behindcount'], label='topic.stack.summary.behindcount')
     fm.plain('\n')
 
+    if empty:
+        fm.plain(_("(stack is empty)\n"))
+
     for idx, r in enumerate(stack(repo, branch=branch, topic=topic), 0):
         ctx = repo[r]
         # special case for t0, b0 as it's hard to plugin into rest of the logic

--- a/tests/test-topic-stack.t	Fri Sep 15 22:48:55 2017 +0530
+++ b/tests/test-topic-stack.t	Fri Sep 15 23:13:05 2017 +0530
@@ -67,6 +67,7 @@
   $ hg stack
   ### topic: other
   ### branch: default
+  (stack is empty)
 
   $ hg up foo
   switching to topic foo
@@ -225,6 +226,7 @@
   $ hg topic --clear
   $ hg stack
   ### branch: default
+  (stack is empty)
 
 Test "t#" reference
 -------------------

--- a/tests/test-topic.t	Fri Sep 15 22:48:55 2017 +0530
+++ b/tests/test-topic.t	Fri Sep 15 23:13:05 2017 +0530
@@ -143,6 +143,7 @@
   $ hg stack
   ### topic: narf
   ### branch: default
+  (stack is empty)
 
 Add commits to topic