diff --git a/addons/sale/models/sale.py b/addons/sale/models/sale.py
index baca5d02acb..f471d60b898 100644
--- a/addons/sale/models/sale.py
+++ b/addons/sale/models/sale.py
@@ -1296,7 +1296,7 @@ class SaleOrderLine(models.Model):
     product_uom = fields.Many2one('uom.uom', string='Unit of Measure', domain="[('category_id', '=', product_uom_category_id)]")
     product_uom_category_id = fields.Many2one(related='product_id.uom_id.category_id', readonly=True)
     product_uom_readonly = fields.Boolean(compute='_compute_product_uom_readonly')
-    product_custom_attribute_value_ids = fields.One2many('product.attribute.custom.value', 'sale_order_line_id', string="Custom Values")
+    product_custom_attribute_value_ids = fields.One2many('product.attribute.custom.value', 'sale_order_line_id', string="Custom Values", copy=True)
 
     # M2M holding the values of product.attribute with create_variant field set to 'no_variant'
     # It allows keeping track of the extra_price associated to those attribute values and add them to the SO line description