diff --git a/Backend/src/validators/ChaptersLesson.validator.ts b/Backend/src/validators/ChaptersLesson.validator.ts
index 933a3e1a..45d7687a 100644
--- a/Backend/src/validators/ChaptersLesson.validator.ts
+++ b/Backend/src/validators/ChaptersLesson.validator.ts
@@ -79,7 +79,7 @@ export const UpdateLessonValidator = Joi.object({
         'number.min': 'Duration must be at least 0'
     }),
     sort_order: Joi.number().integer().min(0).optional(),
-    prerequisite_lesson_ids: Joi.array().items(Joi.number().integer().positive()).optional(),
+    prerequisite_lesson_ids: Joi.array().items(Joi.number().integer().positive()).allow(null).optional(),
     is_published: Joi.boolean().optional()
 });