diff --git a/openedx/core/djangoapps/course_live/tests/test_views.py b/openedx/core/djangoapps/course_live/tests/test_views.py
index 495dfccc969a..fd77799c3d48 100644
--- a/openedx/core/djangoapps/course_live/tests/test_views.py
+++ b/openedx/core/djangoapps/course_live/tests/test_views.py
@@ -292,6 +292,38 @@ def test_post_error_messages(self):
         self.assertEqual(content, expected_data)  # noqa: PT009
         self.assertEqual(response.status_code, 400)  # noqa: PT009
 
+    def test_post_missing_provider_type_without_pii_flag(self):
+        """
+        Test a missing provider_type is reported as a 400, with no PII sharing flag set.
+
+        Distinct from `test_post_error_messages`, which enables `CourseAllowPIISharingInLTIFlag`.
+        That flag makes `pii_sharing_allowed` true, which short-circuits the `and` in the view's
+        PII check before the unresolved (None) provider is dereferenced. Without the flag the
+        provider *is* dereferenced, and the view used to raise an AttributeError -- a 500 on the
+        documented 400 path.
+        """
+        response = self._post({})
+
+        self.assertEqual(response.status_code, 400)  # noqa: PT009
+        content = json.loads(response.content.decode('utf-8'))
+        self.assertEqual(content, {'provider_type': ['This field is required.']})  # noqa: PT009
+
+    def test_post_unknown_provider_type_without_pii_flag(self):
+        """
+        Test a provider_type that names no enabled provider is reported as a 400.
+
+        Same unresolved-provider path as above, reached with a provider_type that is present but
+        does not match an enabled provider.
+        """
+        response = self._post({
+            'enabled': True,
+            'provider_type': 'not_a_real_provider',
+        })
+
+        self.assertEqual(response.status_code, 400)  # noqa: PT009
+        content = json.loads(response.content.decode('utf-8'))
+        self.assertIn('does not exist', str(content))  # noqa: PT009
+
     def test_non_staff_user_access(self):
         """
         Test non staff user has no access to API
diff --git a/openedx/core/djangoapps/course_live/views.py b/openedx/core/djangoapps/course_live/views.py
index a25358571f4c..b47e9c72c153 100644
--- a/openedx/core/djangoapps/course_live/views.py
+++ b/openedx/core/djangoapps/course_live/views.py
@@ -116,7 +116,10 @@ def post(self, request, course_id: str) -> Response:
         """
         pii_sharing_allowed = get_lti_pii_sharing_state_for_course(course_id)
         provider = ProviderManager().get_enabled_providers().get(request.data.get('provider_type', ''), None)
-        if not pii_sharing_allowed and provider.requires_pii_sharing():
+        # `provider` is None when `provider_type` is missing or names a provider that is not
+        # enabled. Let the serializer report that as a 400 rather than raising an AttributeError
+        # here -- the check below already treats `provider` as optional.
+        if not pii_sharing_allowed and provider and provider.requires_pii_sharing():
             return Response({
                 "pii_sharing_allowed": pii_sharing_allowed,
                 "message": "PII sharing is not allowed on this course"