diff --git a/lms/djangoapps/discussion/django_comment_client/base/tests.py b/lms/djangoapps/discussion/django_comment_client/base/tests.py
index 1d695e5232..de936ae575 100644
--- a/lms/djangoapps/discussion/django_comment_client/base/tests.py
+++ b/lms/djangoapps/discussion/django_comment_client/base/tests.py
@@ -111,7 +111,7 @@ class CreateThreadGroupIdTestCase(
             mock_request,
             "cohorted_topic",
             self.student,
-            None
+            ''
         )
         self._assert_json_response_contains_group_info(response)
 
diff --git a/lms/djangoapps/discussion/django_comment_client/tests/group_id.py b/lms/djangoapps/discussion/django_comment_client/tests/group_id.py
index 32b62414a4..9c305cd8ac 100644
--- a/lms/djangoapps/discussion/django_comment_client/tests/group_id.py
+++ b/lms/djangoapps/discussion/django_comment_client/tests/group_id.py
@@ -69,7 +69,7 @@ class CohortedTopicGroupIdTestMixin(GroupIdAssertionMixin):
         pass
 
     def test_cohorted_topic_student_without_group_id(self, mock_request):
-        self.call_view(mock_request, "cohorted_topic", self.student, None, pass_group_id=False)
+        self.call_view(mock_request, "cohorted_topic", self.student, '', pass_group_id=False)
         self._assert_comments_service_called_with_group_id(mock_request, self.student_cohort.id)
 
     def test_cohorted_topic_student_none_group_id(self, mock_request):
@@ -85,7 +85,7 @@ class CohortedTopicGroupIdTestMixin(GroupIdAssertionMixin):
         self._assert_comments_service_called_with_group_id(mock_request, self.student_cohort.id)
 
     def test_cohorted_topic_moderator_without_group_id(self, mock_request):
-        self.call_view(mock_request, "cohorted_topic", self.moderator, None, pass_group_id=False)
+        self.call_view(mock_request, "cohorted_topic", self.moderator, '', pass_group_id=False)
         self._assert_comments_service_called_without_group_id(mock_request)
 
     def test_cohorted_topic_moderator_none_group_id(self, mock_request):
@@ -133,11 +133,11 @@ class NonCohortedTopicGroupIdTestMixin(GroupIdAssertionMixin):
         pass
 
     def test_non_cohorted_topic_student_without_group_id(self, mock_request):
-        self.call_view(mock_request, "non_cohorted_topic", self.student, None, pass_group_id=False)
+        self.call_view(mock_request, "non_cohorted_topic", self.student, '', pass_group_id=False)
         self._assert_comments_service_called_without_group_id(mock_request)
 
     def test_non_cohorted_topic_student_none_group_id(self, mock_request):
-        self.call_view(mock_request, "non_cohorted_topic", self.student, None)
+        self.call_view(mock_request, "non_cohorted_topic", self.student, '')
         self._assert_comments_service_called_without_group_id(mock_request)
 
     def test_non_cohorted_topic_student_with_own_group_id(self, mock_request):
@@ -149,11 +149,11 @@ class NonCohortedTopicGroupIdTestMixin(GroupIdAssertionMixin):
         self._assert_comments_service_called_without_group_id(mock_request)
 
     def test_non_cohorted_topic_moderator_without_group_id(self, mock_request):
-        self.call_view(mock_request, "non_cohorted_topic", self.moderator, None, pass_group_id=False)
+        self.call_view(mock_request, "non_cohorted_topic", self.moderator, '', pass_group_id=False)
         self._assert_comments_service_called_without_group_id(mock_request)
 
     def test_non_cohorted_topic_moderator_none_group_id(self, mock_request):
-        self.call_view(mock_request, "non_cohorted_topic", self.moderator, None)
+        self.call_view(mock_request, "non_cohorted_topic", self.moderator, '')
         self._assert_comments_service_called_without_group_id(mock_request)
 
     def test_non_cohorted_topic_moderator_with_own_group_id(self, mock_request):
@@ -176,6 +176,6 @@ class NonCohortedTopicGroupIdTestMixin(GroupIdAssertionMixin):
         )
 
         team.add_user(self.student)
-        self.call_view(mock_request, team.discussion_topic_id, self.student, None)
+        self.call_view(mock_request, team.discussion_topic_id, self.student, '')
 
         self._assert_comments_service_called_without_group_id(mock_request)
diff --git a/lms/djangoapps/discussion/tests/test_views.py b/lms/djangoapps/discussion/tests/test_views.py
index 1e19c7bf31..0fe34381fe 100644
--- a/lms/djangoapps/discussion/tests/test_views.py
+++ b/lms/djangoapps/discussion/tests/test_views.py
@@ -698,7 +698,7 @@ class SingleThreadAccessTestCase(CohortedTestCase):
                 mock_request,
                 'non_cohorted_topic',
                 user_not_in_team,
-                None
+                ''
             )
             self.assertEqual(403, response.status_code)
             self.assertEqual(