diff --git a/partner_vat_unique/models/res_partner.py b/partner_vat_unique/models/res_partner.py
index 725a6ee78..428b7bdb7 100644
--- a/partner_vat_unique/models/res_partner.py
+++ b/partner_vat_unique/models/res_partner.py
@@ -1,7 +1,7 @@
 # Copyright 2017 Grant Thornton Spain - Ismael Calvo <ismael.calvo@es.gt.com>
 # License AGPL-3.0 or later (http://www.gnu.org/licenses/agpl.html).
 
-from odoo import api, models, _
+from odoo import _, api, fields, models
 from odoo.exceptions import ValidationError
 from odoo.tools import config
 
@@ -9,6 +9,8 @@ from odoo.tools import config
 class ResPartner(models.Model):
     _inherit = 'res.partner'
 
+    vat = fields.Char(copy=False)
+
     @api.constrains('vat')
     def _check_vat_unique(self):
         for record in self:
diff --git a/partner_vat_unique/tests/test_vat_unique.py b/partner_vat_unique/tests/test_vat_unique.py
index 104303ee8..8eea96176 100644
--- a/partner_vat_unique/tests/test_vat_unique.py
+++ b/partner_vat_unique/tests/test_vat_unique.py
@@ -21,3 +21,7 @@ class TestVatUnique(SavepointCase):
                 'name': 'Second partner',
                 'vat': 'ESA12345674'
             })
+
+    def test_duplicate_partner(self):
+        partner_copied = self.partner.copy()
+        self.assertFalse(partner_copied.vat)