diff --git a/addons/account_voucher/invoice.py b/addons/account_voucher/invoice.py
index 426027f984c..af8405c1ec9 100644
--- a/addons/account_voucher/invoice.py
+++ b/addons/account_voucher/invoice.py
@@ -40,7 +40,7 @@ class invoice(osv.osv):
             'target': 'new',
             'domain': '[]',
             'context': {
-                'default_partner_id': self._find_partner(inv),
+                'default_partner_id': self._find_partner(inv).id,
                 'default_amount': inv.type in ('out_refund', 'in_refund') and -inv.residual or inv.residual,
                 'default_number':inv.name,
                 'close_after_process': True,