diff --git a/VirtoCommerce.Storefront.Model/Catalog/Specifications/ProductIsAvailableSpecification.cs b/VirtoCommerce.Storefront.Model/Catalog/Specifications/ProductIsAvailableSpecification.cs
index 21667c6..3e745b9 100644
--- a/VirtoCommerce.Storefront.Model/Catalog/Specifications/ProductIsAvailableSpecification.cs
+++ b/VirtoCommerce.Storefront.Model/Catalog/Specifications/ProductIsAvailableSpecification.cs
@@ -18,10 +18,10 @@ public virtual bool IsSatisfiedBy(long requestedQuantity)
             if (result && _product.TrackInventory)
             {
                 result = _product.Inventory != null &&
-                    _product.AvailableQuantity +
-                    (Convert.ToInt32(_product.Inventory.AllowPreorder) * _product.Inventory.PreorderQuantity) +
-                    (Convert.ToInt32(_product.Inventory.AllowBackorder) * _product.Inventory.BackorderQuantity)
-                    >= requestedQuantity;
+                         _product.AvailableQuantity +
+                         (Convert.ToInt32(_product.Inventory.AllowPreorder) * Convert.ToInt32(_product.Inventory.PreorderQuantity)) +
+                         (Convert.ToInt32(_product.Inventory.AllowBackorder) * Convert.ToInt32(_product.Inventory.BackorderQuantity))
+                         >= requestedQuantity;
             }
 
             return result;
diff --git a/VirtoCommerce.Storefront.Model/Catalog/Specifications/ProductIsInStockSpecification.cs b/VirtoCommerce.Storefront.Model/Catalog/Specifications/ProductIsInStockSpecification.cs
index 0790bda..96894c3 100644
--- a/VirtoCommerce.Storefront.Model/Catalog/Specifications/ProductIsInStockSpecification.cs
+++ b/VirtoCommerce.Storefront.Model/Catalog/Specifications/ProductIsInStockSpecification.cs
@@ -12,8 +12,8 @@ public virtual bool IsSatisfiedBy(Product product)
             {
                 result = product.Inventory != null &&
                     product.AvailableQuantity +
-                    (Convert.ToInt32(product.Inventory.AllowPreorder) * product.Inventory.PreorderQuantity) +
-                    (Convert.ToInt32(product.Inventory.AllowBackorder) * product.Inventory.BackorderQuantity)
+                    (Convert.ToInt32(product.Inventory.AllowPreorder) * Convert.ToInt32(product.Inventory.PreorderQuantity)) +
+                    (Convert.ToInt32(product.Inventory.AllowBackorder) * Convert.ToInt32(product.Inventory.BackorderQuantity))
                     > 0;
             }
             return result;