diff --git a/make_post_sell/views/product.py b/make_post_sell/views/product.py
index 0911940..3f2b2b6 100644
--- a/make_post_sell/views/product.py
+++ b/make_post_sell/views/product.py
@@ -340,7 +340,7 @@ def product_edit(request):
             .all()
         )
         inventories = {
-            inv.shop_location_id: inv.quantity for inv in product.inventories
+            inv.shop_location.id: inv.quantity for inv in product.inventories
         }
 
     return {
@@ -364,19 +364,33 @@ def product_inventory_edit(request):
         request.session.flash(("This product is not physical.", "error"))
         return HTTPFound(get_referer_or_home(request))
 
-    for inventory in product.inventories:
-        quantity = request.params.get(f"inventory_{inventory.shop_location.id}", None)
+    # Get all shop locations for the product's shop
+    shop_locations = request.shop.shop_locations
+
+    updated = False
+
+    for location in shop_locations:
+        quantity = request.params.get(f"inventory_{location.id}", None)
         if quantity is not None:
             try:
                 quantity = int(quantity)
-                inventory.update_quantity(quantity)
+                inventory = next((inv for inv in product.inventories if inv.shop_location_id == location.id), None)
+                if inventory:
+                    if inventory.quantity != quantity:
+                        inventory.update_quantity(quantity)
+                        request.dbsession.add(inventory)
+                        updated = True
+                else:
+                    inventory = Inventory(shop_location=location, product=product, quantity=quantity)
+                    request.dbsession.add(inventory)
+                    updated = True
             except ValueError:
-                request.session.flash(
-                    (f"Invalid quantity for location {inventory.shop_location.name}.", "error")
-                )
+                request.session.flash((f"Invalid quantity for location {location.name}.", "error"))
+
+    if updated:
+        request.dbsession.flush()
+        request.session.flash(("Inventory updated successfully.", "success"))
 
-    request.dbsession.flush()
-    request.session.flash(("Inventory updated successfully.", "success"))
     return HTTPFound(get_referer_or_home(request))