diff --git a/shopinvader_api_cart/schemas/amount.py b/shopinvader_api_cart/schemas/amount.py
index e47d74a9a0..6a964d527b 100644
--- a/shopinvader_api_cart/schemas/amount.py
+++ b/shopinvader_api_cart/schemas/amount.py
@@ -28,34 +28,25 @@ def from_sale_order(cls, sale_order):
         )
 
     @classmethod
-    def from_sale_order_line(cls, order_line):
+    def from_sale_order_line(cls, order_line, **kwargs):
         precision = order_line.order_id.currency_id.decimal_places
-        res = cls.model_construct()
-        res.discount_total = float_round(order_line.discount_total, precision)
-        res.total_without_discount = float_round(
-            order_line.price_total_no_discount, precision
+        return cls(
+            discount_total=float_round(order_line.discount_total, precision),
+            total_without_discount=float_round(
+                order_line.price_total_no_discount, precision
+            ),
+            tax=float_round(order_line.price_tax, precision),
+            untaxed=float_round(order_line.price_subtotal, precision),
+            total=float_round(order_line.price_total, precision),
+            **kwargs
         )
-        res.tax = float_round(order_line.price_tax, precision)
-        res.untaxed = float_round(order_line.price_subtotal, precision)
-        res.total = float_round(order_line.price_total, precision)
-        return res
-        # FIXME: cannot use cls(...) when Pydantic model is extended.
-        # return cls(
-        #     discount_total=float_round(order_line.discount_total, precision),
-        #     total_without_discount=float_round(
-        #         order_line.price_total_no_discount, precision
-        #     ),
-        #     tax=float_round(order_line.price_tax, precision),
-        #     untaxed=float_round(order_line.price_subtotal, precision),
-        #     total=float_round(order_line.price_total, precision),
-        # )
 
 
 class SaleLineAmount(SaleAmount):
     price: float = Field(description="Unit price")
 
     @classmethod
-    def from_sale_order_line(cls, order_line):
-        res = super().from_sale_order_line(order_line)
-        res.price = order_line.price_unit
+    def from_sale_order_line(cls, order_line, **kwargs):
+        kwargs["price"] = order_line.price_unit
+        res = super().from_sale_order_line(order_line, **kwargs)
         return res