diff --git a/golem_resource_account/models/golem_resource_reservation.py b/golem_resource_account/models/golem_resource_reservation.py
index 0b4492b..556100b 100644
--- a/golem_resource_account/models/golem_resource_reservation.py
+++ b/golem_resource_account/models/golem_resource_reservation.py
@@ -27,11 +27,12 @@ class GolemResourceReservation(models.Model):
     _inherit = 'golem.resource.reservation'
 
     resource_product_id = fields.Many2one(related='resource_id.product_tmpl_id')
-    invoice_line_id = fields.Many2one('account.invoice.line')
+    invoice_line_id = fields.Many2one('account.invoice.line', copy=False)
     invoice_line_price_subtotal = fields.Monetary(related='invoice_line_id.price_subtotal')
     invoice_id = fields.Many2one(related='invoice_line_id.invoice_id',
                                  string='Invoice')
-    invoice_state = fields.Selection(related='invoice_id.state', store=True)
+    invoice_state = fields.Selection(related='invoice_id.state', store=True,
+                                     copy=False)
     invoice_amount_total = fields.Monetary(related='invoice_id.amount_total')
     currency_id = fields.Many2one(related='invoice_id.currency_id')