diff --git a/openedx/core/djangoapps/enrollments/serializers.py b/openedx/core/djangoapps/enrollments/serializers.py
index decd06e218bb..7a0a68d2e93d 100644
--- a/openedx/core/djangoapps/enrollments/serializers.py
+++ b/openedx/core/djangoapps/enrollments/serializers.py
@@ -38,10 +38,13 @@ class CourseSerializer(serializers.Serializer):  # pylint: disable=abstract-meth
 
     course_id = serializers.CharField(source="id")
     course_name = serializers.CharField(source="display_name_with_default")
-    enrollment_start = serializers.DateTimeField(format=None)
-    enrollment_end = serializers.DateTimeField(format=None)
-    course_start = serializers.DateTimeField(source="start", format=None)
-    course_end = serializers.DateTimeField(source="end", format=None)
+    # These are null for courses with no dates set, so they must be declared
+    # nullable — otherwise the published schema tells every generated client
+    # the fields are always present and parsing null raises.
+    enrollment_start = serializers.DateTimeField(format=None, allow_null=True)
+    enrollment_end = serializers.DateTimeField(format=None, allow_null=True)
+    course_start = serializers.DateTimeField(source="start", format=None, allow_null=True)
+    course_end = serializers.DateTimeField(source="end", format=None, allow_null=True)
     invite_only = serializers.BooleanField(source="invitation_only")
     course_modes = serializers.SerializerMethodField()
     pacing_type = serializers.SerializerMethodField()
diff --git a/openedx/core/djangoapps/enrollments/v2/views.py b/openedx/core/djangoapps/enrollments/v2/views.py
index 4b13e247d8f6..f5f192a521f8 100644
--- a/openedx/core/djangoapps/enrollments/v2/views.py
+++ b/openedx/core/djangoapps/enrollments/v2/views.py
@@ -402,6 +402,10 @@ def unenroll(self, request):
         url_path="enrollment_allowed",
         permission_classes=[permissions.IsAdminUser],
         throttle_classes=[EnrollmentUserThrottle],
+        # GET returns a plain list. Actions inherit the viewset's
+        # pagination_class, which would otherwise make drf-spectacular publish
+        # a paginated envelope this endpoint never returns.
+        pagination_class=None,
     )
     def allowed(self, request):
         """Retrieve, create, or delete CourseEnrollmentAllowed records. Admin-only."""