diff --git a/addons/account/models/account_invoice.py b/addons/account/models/account_invoice.py
index 4caeb61d2ee..ec7cca76b2b 100644
--- a/addons/account/models/account_invoice.py
+++ b/addons/account/models/account_invoice.py
@@ -304,7 +304,7 @@ class AccountInvoice(models.Model):
              "means direct payment.")
     partner_id = fields.Many2one('res.partner', string='Partner', change_default=True,
         readonly=True, states={'draft': [('readonly', False)]},
-        track_visibility='always', help="You can find a contact by its Name, TIN, Email or Internal Reference.")
+        track_visibility='always', ondelete='restrict', help="You can find a contact by its Name, TIN, Email or Internal Reference.")
     vendor_bill_id = fields.Many2one('account.invoice', string='Vendor Bill',
         help="Auto-complete from a past bill.")
     payment_term_id = fields.Many2one('account.payment.term', string='Payment Terms', oldname='payment_term',