diff --git a/openedx/core/djangoapps/content_libraries/collections/rest_api/v1/views.py b/openedx/core/djangoapps/content_libraries/collections/rest_api/v1/views.py
index ef381c5da73..b9ba32e9037 100644
--- a/openedx/core/djangoapps/content_libraries/collections/rest_api/v1/views.py
+++ b/openedx/core/djangoapps/content_libraries/collections/rest_api/v1/views.py
@@ -225,7 +225,7 @@ def update_contents(self, request, lib_key_str, pk=None):
             count = authoring_api.add_to_collections(collections_qset, contents_qset)
 
         # Emit a CONTENT_OBJECT_TAGS_CHANGED event for each of the objects added/removed
-        object_ids = contents_qset.values_list("pk", flat=True)
+        object_ids = contents_qset.values_list("key", flat=True)
         for object_id in object_ids:
             CONTENT_OBJECT_TAGS_CHANGED.send_event(
                 content_object=ContentObjectData(object_id=object_id),