--- a/hgext3rd/evolve/__init__.py	Fri Jul 14 01:32:34 2017 +0200
+++ b/hgext3rd/evolve/__init__.py	Fri Jul 14 01:49:43 2017 +0200
@@ -2002,7 +2002,30 @@
                 lockmod.release(tr, lock)
 
     displayer.show(target)
-    return 0
+
+def _findprevtarget(repo, displayer, movebookmark=False, topic=True):
+    target = bookmark = None
+    wkctx = repo[None]
+    wparents = wkctx.parents()
+    parents = wparents[0].parents()
+    currenttopic = getattr(repo, 'currenttopic', '')
+    if currenttopic and topic:
+        parents = [ctx for ctx in parents if ctx.topic() == currenttopic]
+    if wparents[0].node() == node.nullid:
+        repo.ui.warn(_('already at repository root\n'))
+    elif not parents and currenttopic:
+        repo.ui.warn(_('no parent in topic "%s"\n') % currenttopic)
+        repo.ui.warn(_('(do you want --no-topic)\n'))
+    elif len(parents) == 1:
+        target = parents[0]
+        bookmark = None
+        if movebookmark:
+            bookmark = repo._activebookmark
+    else:
+        for p in parents:
+            displayer.show(p)
+        repo.ui.warn(_('multiple parents, explicitly update to one\n'))
+    return target, bookmark
 
 @eh.command(
     '^previous',
@@ -2033,27 +2056,15 @@
                 exc.hint = _('do you want --merge?')
                 raise
 
-        parents = wparents[0].parents()
-        topic = getattr(repo, 'currenttopic', '')
-        if topic and not opts.get("no_topic", False):
-            parents = [ctx for ctx in parents if ctx.topic() == topic]
         displayer = cmdutil.show_changeset(ui, repo, {'template': shorttemplate})
-        if wparents[0].node() == node.nullid:
-            ui.warn(_('already at repository root\n'))
-            return 1
-        elif not parents and topic:
-            ui.warn(_('no parent in topic "%s"\n') % topic)
-            ui.warn(_('(do you want --no-topic)\n'))
-        elif len(parents) == 1:
-            target = parents[0]
-            bookmark = None
-            if opts.get('move_bookmark'):
-                bookmark = repo._activebookmark
-            return _prevupdate(repo, displayer, target, bookmark, dryrunopt)
+
+        target, bookmark = _findprevtarget(repo, displayer,
+                                           opts.get('move_bookmark'),
+                                           not opts.get("no_topic", False))
+        if target is not None:
+            _prevupdate(repo, displayer, target, bookmark, dryrunopt)
+            return 0
         else:
-            for p in parents:
-                displayer.show(p)
-            ui.warn(_('multiple parents, explicitly update to one\n'))
             return 1
     finally:
         lockmod.release(wlock)

--- a/tests/test-evolve-topic.t	Fri Jul 14 01:32:34 2017 +0200
+++ b/tests/test-evolve-topic.t	Fri Jul 14 01:49:43 2017 +0200
@@ -211,6 +211,7 @@
   $ hg prev
   no parent in topic "bar"
   (do you want --no-topic)
+  [1]
   $ hg prev --no-topic
   switching to topic foo
   0 files updated, 0 files merged, 1 files removed, 0 files unresolved