diff --git a/product.py b/product.py
index 0f05618458..b9e6bed8e3 100644
--- a/product.py
+++ b/product.py
@@ -476,7 +476,7 @@ class ProductCostPrice(ModelSQL, CompanyValueMixin):
     @classmethod
     def _migrate_property(cls, field_names, value_names, fields):
         field_names.append('cost_price')
-        value_names.extend('cost_price')
+        value_names.append('cost_price')
         fields.append('company')
         migrate_property(
             'product.template', field_names, cls, value_names,