diff --git a/catalog_microservice/data/use_cases/product_update_stock.py b/catalog_microservice/data/use_cases/product_update_stock.py
index 1b2f606..c26545c 100644
--- a/catalog_microservice/data/use_cases/product_update_stock.py
+++ b/catalog_microservice/data/use_cases/product_update_stock.py
@@ -26,6 +26,11 @@ def __validate_stock(self, stock):
         
     def __update_stock(self, product_id, stock):
         try:
+            product = self.product_repository.select_product(product_id)
+            
+            if product.stock - stock < 0:
+                raise ValueError("Stock cannot be negative for product with id {}".format(product_id))
+            
             self.product_repository.update_stock(product_id, stock)
         except ProductNotFoundError as e:
             raise HttpNotFoundError(str(e))
diff --git a/catalog_microservice/infra/database/repositories/products_repository.py b/catalog_microservice/infra/database/repositories/products_repository.py
index d03e8dc..efe6592 100644
--- a/catalog_microservice/infra/database/repositories/products_repository.py
+++ b/catalog_microservice/infra/database/repositories/products_repository.py
@@ -76,7 +76,7 @@ def update_stock(cls, product_id: str, stock: int):
                 product = db_connection.session.query(ProductsEntity).filter(ProductsEntity.id == product_id).first()
                 if not product:
                     raise ProductNotFoundError(product_id=product_id)
-                product.stock = stock
+                product.stock = product.stock - stock
                 db_connection.session.commit()
             except ProductNotFoundError as e:
                 db_connection.session.rollback()