diff --git a/CHANGES.txt b/CHANGES.txt
index 3071d6f..0daa1bd 100644
--- a/CHANGES.txt
+++ b/CHANGES.txt
@@ -4,15 +4,18 @@ Changelog
 2.1.5 (unreleased)
 ------------------
 
-- Redirect to "/view" for Image, File and anything listed as requiring 
+- Redirect to "/view" for Image, File and anything listed as requiring
   a view in the url to properly display comments.
   [eleddy]
 
-
 - Make comments and controlpanel views more robust, so they don't break if no
   workflow is assigned to the 'Discussion Item' content type.
   [timo]
 
+- Warning message added to discussion control panel that shows up if there are
+  unmigrated comments.
+  [timo]
+
 
 2.1.4 (2012-02-29)
 ------------------
@@ -78,15 +81,15 @@ Changelog
 - New feature: Markdown syntax added to possible comment text transforms.
   [timo]
 
-- Make sure the comment brains are updated properly when the content object is 
+- Make sure the comment brains are updated properly when the content object is
   renamed.
   [hannosch, timo]
 
 - Make sure only comments to the content object are removed from the catalog
   when the content object is moved.
   [hannosch, timo, davisagli]
-  
-- Make sure the conversation.getComments method returns acquisition wrapped 
+
+- Make sure the conversation.getComments method returns acquisition wrapped
   comments.
   [timo]
 
@@ -100,7 +103,7 @@ Changelog
 2.0.9 (2011-07-25)
 ------------------
 
-- Make sure the creator index always stores utf-8 encoded stings and not 
+- Make sure the creator index always stores utf-8 encoded stings and not
   unicode.
   [timo]
 
@@ -112,7 +115,7 @@ Changelog
   fixes http://dev.plone.org/plone/ticket/11298.
   [timo]
 
-- Use Plone's safe_encode method instead of encode() for the creator index to 
+- Use Plone's safe_encode method instead of encode() for the creator index to
   make sure unicode encoded strings can be indexed too.
   [timo]
 
@@ -120,7 +123,7 @@ Changelog
 2.0.7 (2011-07-15)
 ------------------
 
-- Fix discussion control panel submit for Google Chrome. This fixes 
+- Fix discussion control panel submit for Google Chrome. This fixes
   http://dev.plone.org/plone/ticket/11486.
 
 
@@ -130,7 +133,7 @@ Changelog
 - Update comment brains in zcatalog when moving a content object with comments.
   This fixes http://dev.plone.org/plone/ticket/11331.
   [timo]
-  
+
 - Plone 3 specific exclusion of plone.app.uuid removed.
   [timo]
 
@@ -143,7 +146,7 @@ Changelog
   imported after collapsibleformfields.js.
   [elro]
 
-- Enable the left-menu on the configlet, to be more consistent with all other 
+- Enable the left-menu on the configlet, to be more consistent with all other
   configlets. Related to http://dev.plone.org/plone/ticket/11737
   [WouterVH]
 
@@ -159,7 +162,7 @@ Changelog
 - Refactor/clean up the handleComment method.
   [timo]
 
-- Make handleComment method store comment attributes from form extenders. This 
+- Make handleComment method store comment attributes from form extenders. This
   allows us to extend the comment form with external add-ons. See
   http://packages.python.org/plone.app.discussion/howtos/howto_extend_the_comment_form.html
   for details.
diff --git a/plone/app/discussion/browser/controlpanel.pt b/plone/app/discussion/browser/controlpanel.pt
index 46cf9e9..106b6d2 100644
--- a/plone/app/discussion/browser/controlpanel.pt
+++ b/plone/app/discussion/browser/controlpanel.pt
@@ -61,6 +61,25 @@
         </dd>
     </dl>
 
+    <dl class="portalMessage warning"
+        tal:condition="view/unmigrated_comments_warning">
+        <dt i18n:translate="">
+            Warning
+        </dt>
+        <dd i18n:translate="text_unmigrated_comments">
+            You have comments that have not been migrated to the new
+            commenting system that has been introduced in Plone 4.1.
+            Please
+            <tal:link i18n:name="label_comments_migration_link">
+                <a href=""
+                   i18n:translate="text_comments_migration_link"
+                   tal:attributes="href string:${portal_url}/@@comment-migration"
+                >migrate your comments</a>
+            </tal:link>
+            to fix this.
+        </dd>
+    </dl>
+
     <div metal:use-macro="context/global_statusmessage/macros/portal_message">
       Portal status message
     </div>
diff --git a/plone/app/discussion/browser/controlpanel.py b/plone/app/discussion/browser/controlpanel.py
index f993612..67e5c14 100644
--- a/plone/app/discussion/browser/controlpanel.py
+++ b/plone/app/discussion/browser/controlpanel.py
@@ -4,6 +4,8 @@ from Acquisition import aq_base, aq_inner
 
 from Products.CMFCore.utils import getToolByName
 
+from Products.CMFCore.interfaces._content import IDiscussionResponse
+
 from Products.Five.browser.pagetemplatefile import ViewPageTemplateFile
 
 from Products.statusmessages.interfaces import IStatusMessage
@@ -155,6 +157,15 @@ class DiscussionSettingsControlPanel(controlpanel.ControlPanelFormWrapper):
             return
         return True
 
+    def unmigrated_comments_warning(self):
+        """Returns true if site contains unmigrated comments.
+        """
+        catalog = getToolByName(aq_inner(self.context), 'portal_catalog', None)
+        count_comments_old = catalog.searchResults(
+            object_provides=IDiscussionResponse.__identifier__)
+        if count_comments_old:
+            return True
+
 
 def notify_configuration_changed(event):
     """Event subscriber that is called every time the configuration changed.