diff --git a/shop/api/v1/viewsets.py b/shop/api/v1/viewsets.py
index b73b0ec..ec33996 100644
--- a/shop/api/v1/viewsets.py
+++ b/shop/api/v1/viewsets.py
@@ -40,6 +40,7 @@ from shop.models import (
 )
 
 from shop.api.v1.permissions import ProductPermissions, ProductPricePermissions
+from shop.utils import delete_product_batch
 
 
 class ProductViewSet(ModelViewSet):
@@ -107,10 +108,16 @@ class ProductBatchViewSet(ModelViewSet):
         product.save()
 
     def perform_destroy(self, instance):
+        delete_product_batch(instance)
+
+    def perform_update(self, serializer):
+        instance = self.get_object()
         product = instance.product
-        product.stock = max(product.stock - instance.quantity, 0)
+        product.stock -= instance.quantity
+
+        updated_batch = serializer.save()
+        product.stock += updated_batch.quantity
         product.save()
-        instance.delete()
 
 
 class CustomerViewSet(ModelViewSet):
diff --git a/shop/tests/test_api_product_batches.py b/shop/tests/test_api_product_batches.py
index 965095d..04a83f4 100644
--- a/shop/tests/test_api_product_batches.py
+++ b/shop/tests/test_api_product_batches.py
@@ -51,6 +51,8 @@ class TestProductBatchesAPI(APITestCase, TestUserAuthenticationMixin):
         pk = response.data.get("id")
 
         response = self.client.get(f"/api/v1/shop/product-batches/{pk}/")
+        self.product.refresh_from_db()
+        assert self.product.stock == Decimal("5")
         assert response.status_code == status.HTTP_200_OK
 
     def test_create_update_product_batch(self):
@@ -73,6 +75,9 @@ class TestProductBatchesAPI(APITestCase, TestUserAuthenticationMixin):
         response = self.client.get(f"/api/v1/shop/product-batches/{pk}/")
         assert response.status_code == status.HTTP_200_OK
 
+        self.product.refresh_from_db()
+        assert self.product.stock == Decimal("5")
+
         response = self.client.patch(
             f"/api/v1/shop/product-batches/{pk}/",
             {
@@ -81,6 +86,9 @@ class TestProductBatchesAPI(APITestCase, TestUserAuthenticationMixin):
         )
         assert response.status_code == status.HTTP_200_OK
 
+        self.product.refresh_from_db()
+        assert self.product.stock == Decimal("10")
+
         response = self.client.get(f"/api/v1/shop/product-batches/{pk}/")
         assert response.status_code == status.HTTP_200_OK
         assert Decimal(response.data.get("quantity")) == Decimal("10")
diff --git a/shop/utils.py b/shop/utils.py
index 9440675..e2c0216 100644
--- a/shop/utils.py
+++ b/shop/utils.py
@@ -1,6 +1,6 @@
 from decimal import Decimal
 
-from shop.models import OrderLine, Product, Order, Customer
+from shop.models import OrderLine, Product, Order, Customer, ProductBatch
 
 
 def create_order_line_for_product(product: Product, quantity: Decimal, order: Order):
@@ -61,3 +61,10 @@ def create_order(
     )
 
     return order
+
+
+def delete_product_batch(batch: ProductBatch):
+    product = batch.product
+    product.stock = max(product.stock - batch.quantity, 0)
+    product.save()
+    batch.delete()