diff --git a/addons/website_slides/controllers/mail.py b/addons/website_slides/controllers/mail.py
index a43615e016e..e6bcd2ff0da 100644
--- a/addons/website_slides/controllers/mail.py
+++ b/addons/website_slides/controllers/mail.py
@@ -4,8 +4,9 @@
 import werkzeug
 
 from werkzeug.exceptions import NotFound, Forbidden
+from odoo.exceptions import ValidationError
 
-from odoo import http, _
+from odoo import _, http
 from odoo.http import request
 from odoo.addons.portal.controllers.mail import _check_special_access, PortalChatter
 from odoo.tools import plaintext2html, html2plaintext
@@ -22,12 +23,18 @@ class SlidesPortalChatter(PortalChatter):
 
     @http.route()
     def portal_chatter_post(self, res_model, res_id, message, **kw):
+        previous_post = request.env['mail.message'].search([('res_id', '=', res_id),
+                                                            ('author_id', '=', request.env.user.partner_id.id),
+                                                            ('model', '=', 'slide.channel'),
+                                                            ('subtype_id', '=', request.env.ref('mail.mt_comment').id)])
+        if previous_post:
+            raise ValidationError(_("Only a single review can be posted per course."))
+
         result = super(SlidesPortalChatter, self).portal_chatter_post(res_model, res_id, message, **kw)
         if result and res_model == 'slide.channel':
             rating_value = kw.get('rating_value', False)
             slide_channel = request.env[res_model].sudo().browse(int(res_id))
             if rating_value and slide_channel and request.env.user.partner_id.id == int(kw.get('pid')):
-                # apply karma gain rule only once
                 request.env.user._add_karma(slide_channel.karma_gen_channel_rank, slide_channel, _('Course Ranked'))
             result.update({
                 'default_rating_value': rating_value,
diff --git a/addons/website_slides/i18n/website_slides.pot b/addons/website_slides/i18n/website_slides.pot
index a0c17a86d43..6ae13230360 100644
--- a/addons/website_slides/i18n/website_slides.pot
+++ b/addons/website_slides/i18n/website_slides.pot
@@ -4412,6 +4412,12 @@ msgstr ""
 msgid "Operation not supported"
 msgstr ""
 
+#. module: website_slides
+#: code:addons/website_slides/controllers/mail.py:0
+#, python-format
+msgid "Only a single review can be posted per course."
+msgstr ""
+
 #. module: website_slides
 #: model:ir.model.fields,help:website_slides.field_slide_channel_invite__lang
 msgid ""
diff --git a/addons/website_slides/tests/test_security.py b/addons/website_slides/tests/test_security.py
index aca48b7a1a8..54014bdd30f 100644
--- a/addons/website_slides/tests/test_security.py
+++ b/addons/website_slides/tests/test_security.py
@@ -2,10 +2,11 @@
 # Part of Odoo. See LICENSE file for full copyright and licensing details.
 import base64
 
+from odoo import http
 from odoo.addons.mail.tests.common import mail_new_test_user
 from odoo.addons.website_slides.tests import common
 from odoo.exceptions import AccessError
-from odoo.tests import tagged
+from odoo.tests import tagged, HttpCase
 from odoo.tools import mute_logger
 
 
@@ -528,3 +529,41 @@ class TestAccessFeatures(common.SlidesCase):
         resource2.with_user(self.user_manager).write({'name': 'Another name'})
         resource2.with_user(self.user_manager).unlink()
         self.env['slide.slide.resource'].with_user(self.user_manager).create(resource_values)
+
+
+@tagged('functional')
+class TestReview(common.SlidesCase, HttpCase):
+    @mute_logger('odoo.addons.http_routing.models.ir_http', 'odoo.http')
+    def test_channel_multiple_reviews(self):
+        self.authenticate("admin", "admin")
+
+        res1 = self.opener.post(
+            url='%s/mail/chatter_post' % self.base_url(),
+            json={
+                'params': {
+                    'res_id': self.channel.id,
+                    'res_model': 'slide.channel',
+                    'message': 'My first review :)',
+                    'rating_value': '2',
+                    'pid': self.env.user.partner_id.id,
+                    'csrf_token': http.Request.csrf_token(self),
+                },
+            },
+        )
+        self.assertIn("My first review :)", res1.text)
+
+
+        res2 = self.opener.post(
+            url='%s/mail/chatter_post' % self.base_url(),
+            json={
+                'params': {
+                    'res_id': self.channel.id,
+                    'res_model': 'slide.channel',
+                    'message': 'My second review :)',
+                    'rating_value': '2',
+                    'pid': self.env.user.partner_id.id,
+                    'csrf_token': http.Request.csrf_token(self),
+                },
+            },
+        )
+        self.assertIn("odoo.exceptions.ValidationError", res2.text)