Solucionar secuencia de orden de pago

orden_pago.py

@@ -34,14 +34,10 @@ class OrdenPago(models.Model):
     def _get_user(self):
         return self.env.uid
 
-    def _get_number(self):
-        return self.env['ir.sequence'].next_by_code('orden.pago') or '*'
+    #def _get_number(self):
+    #    return self.env['ir.sequence'].next_by_code('orden.pago') or '*'
 
-    name = fields.Char(
-        string=u'Referencia',
-        readonly=True,
-        default=_get_number,
-    )
+    name = fields.Char(string=u'Referencia', readonly=True, copy=False, default='/')
 
     partner_id = fields.Many2one(
         'res.partner',
@@ -115,6 +111,12 @@ class OrdenPago(models.Model):
         store=True
     )
 
+    @api.model
+    def create(self, vals):
+        if vals.get('name', '/') == '/':
+            vals['name'] = self.env['ir.sequence'].next_by_code('orden.pago') or '/'
+        return super(OrdenPago, self).create(vals)
+
     @api.depends('invoice_ids.amount_total')
     def _compute_total(self):
         for rec in self: