diff --git a/addons/sale/models/sale.py b/addons/sale/models/sale.py
index 3c60e7cb0d9..1dcd6ca3c22 100644
--- a/addons/sale/models/sale.py
+++ b/addons/sale/models/sale.py
@@ -122,7 +122,7 @@ class SaleOrder(models.Model):
     validity_date = fields.Date(string='Expiration Date', readonly=True, copy=False, states={'draft': [('readonly', False)], 'sent': [('readonly', False)]},
         help="Manually set the expiration date of your quotation (offer), or it will set the date automatically based on the template if online quotation is installed.")
     create_date = fields.Datetime(string='Creation Date', readonly=True, index=True, help="Date on which sales order is created.")
-    confirmation_date = fields.Datetime(string='Confirmation Date', readonly=True, index=True, help="Date on which the sale order is confirmed.", oldname="date_confirm")
+    confirmation_date = fields.Datetime(string='Confirmation Date', readonly=True, index=True, help="Date on which the sale order is confirmed.", oldname="date_confirm", copy=False)
     user_id = fields.Many2one('res.users', string='Salesperson', index=True, track_visibility='onchange', default=lambda self: self.env.user)
     partner_id = fields.Many2one('res.partner', string='Customer', readonly=True, states={'draft': [('readonly', False)], 'sent': [('readonly', False)]}, required=True, change_default=True, index=True, track_visibility='always')
     partner_invoice_id = fields.Many2one('res.partner', string='Invoice Address', readonly=True, required=True, states={'draft': [('readonly', False)], 'sent': [('readonly', False)]}, help="Invoice address for current sales order.")