diff --git a/lms/djangoapps/django_comment_client/tests/test_utils.py b/lms/djangoapps/django_comment_client/tests/test_utils.py
index 809641a9fc..24c86b2474 100644
--- a/lms/djangoapps/django_comment_client/tests/test_utils.py
+++ b/lms/djangoapps/django_comment_client/tests/test_utils.py
@@ -25,7 +25,8 @@ from django_comment_client.tests.utils import config_course_discussions, topic_n
 from django_comment_common.models import (
     CourseDiscussionSettings,
     ForumsConfig,
-    assign_role
+    assign_role,
+    DiscussionsIdMapping,
 )
 from django_comment_common.utils import (
     get_course_discussion_settings,
@@ -34,7 +35,6 @@ from django_comment_common.utils import (
 )
 from lms.djangoapps.teams.tests.factories import CourseTeamFactory
 from lms.lib.comment_client.utils import CommentClientMaintenanceError, perform_request
-from openedx.core.djangoapps.content.course_structures.models import CourseStructure
 from openedx.core.djangoapps.course_groups import cohorts
 from openedx.core.djangoapps.course_groups.cohorts import set_course_cohorted
 from openedx.core.djangoapps.course_groups.tests.helpers import CohortFactory, config_course_cohorts
@@ -262,6 +262,7 @@ class CachedDiscussionIdMapTestCase(ModuleStoreTestCase):
             discussion_target='Beta Testing',
             visible_to_staff_only=True
         )
+        RequestCache.clear_request_cache()  # clear the cache before the last course publish
         self.bad_discussion = ItemFactory.create(
             parent_location=self.course.location,
             category='discussion',
@@ -278,14 +279,14 @@ class CachedDiscussionIdMapTestCase(ModuleStoreTestCase):
         usage_key = utils.get_cached_discussion_key(self.course.id, 'bogus_id')
         self.assertIsNone(usage_key)
 
-    def test_cache_raises_exception_if_course_structure_not_cached(self):
-        CourseStructure.objects.all().delete()
+    def test_cache_raises_exception_if_discussion_id_map_not_cached(self):
+        DiscussionsIdMapping.objects.all().delete()
         with self.assertRaises(utils.DiscussionIdMapIsNotCached):
             utils.get_cached_discussion_key(self.course.id, 'test_discussion_id')
 
     def test_cache_raises_exception_if_discussion_id_not_cached(self):
-        cache = CourseStructure.objects.get(course_id=self.course.id)
-        cache.discussion_id_map_json = None
+        cache = DiscussionsIdMapping.objects.get(course_id=self.course.id)
+        cache.mapping = None
         cache.save()
 
         with self.assertRaises(utils.DiscussionIdMapIsNotCached):
@@ -313,7 +314,7 @@ class CachedDiscussionIdMapTestCase(ModuleStoreTestCase):
         self.verify_discussion_metadata()
 
     def test_get_discussion_id_map_without_cache(self):
-        CourseStructure.objects.all().delete()
+        DiscussionsIdMapping.objects.all().delete()
         self.verify_discussion_metadata()
 
     def test_get_missing_discussion_id_map_from_cache(self):
diff --git a/lms/djangoapps/django_comment_client/utils.py b/lms/djangoapps/django_comment_client/utils.py
index abcbf5fa63..3f61c40f61 100644
--- a/lms/djangoapps/django_comment_client/utils.py
+++ b/lms/djangoapps/django_comment_client/utils.py
@@ -9,7 +9,7 @@ from django.urls import reverse
 from django.db import connection
 from django.http import HttpResponse
 from pytz import UTC
-from opaque_keys.edx.keys import CourseKey
+from opaque_keys.edx.keys import CourseKey, UsageKey
 from opaque_keys.edx.locations import i4xEncoder
 from six import text_type
 
@@ -18,9 +18,8 @@ from courseware.access import has_access
 from django_comment_client.constants import TYPE_ENTRY, TYPE_SUBCATEGORY
 from django_comment_client.permissions import check_permissions_by_view, get_team, has_permission
 from django_comment_client.settings import MAX_COMMENT_DEPTH
-from django_comment_common.models import FORUM_ROLE_STUDENT, CourseDiscussionSettings, Role
+from django_comment_common.models import FORUM_ROLE_STUDENT, CourseDiscussionSettings, DiscussionsIdMapping, Role
 from django_comment_common.utils import get_course_discussion_settings
-from openedx.core.djangoapps.content.course_structures.models import CourseStructure
 from openedx.core.djangoapps.course_groups.cohorts import get_cohort_id, get_cohort_names, is_course_cohorted
 from openedx.core.djangoapps.request_cache.middleware import request_cached
 from student.models import get_user_by_username_or_email
@@ -164,12 +163,16 @@ def get_cached_discussion_key(course_id, discussion_id):
     raises a DiscussionIdMapIsNotCached exception.
     """
     try:
-        mapping = CourseStructure.objects.get(course_id=course_id).discussion_id_map
+        mapping = DiscussionsIdMapping.objects.get(course_id=course_id).mapping
         if not mapping:
             raise DiscussionIdMapIsNotCached()
 
-        return mapping.get(discussion_id)
-    except CourseStructure.DoesNotExist:
+        usage_key_string = mapping.get(discussion_id)
+        if usage_key_string:
+            return UsageKey.from_string(usage_key_string).map_into_course(course_id)
+        else:
+            return None
+    except DiscussionsIdMapping.DoesNotExist:
         raise DiscussionIdMapIsNotCached()