diff --git a/product_contract/models/contract_line.py b/product_contract/models/contract_line.py
index 2a85f73e7..96978a895 100644
--- a/product_contract/models/contract_line.py
+++ b/product_contract/models/contract_line.py
@@ -19,9 +19,9 @@ class ContractLine(models.Model):
     display_name = fields.Char(compute='_compute_display_name_2')
 
     @api.multi
-    def _prepare_invoice_line(self, invoice_id=False):
+    def _prepare_invoice_line(self, invoice_id=False, invoice_values=False):
         res = super(ContractLine, self)._prepare_invoice_line(
-            invoice_id=invoice_id
+            invoice_id=invoice_id, invoice_values=invoice_values,
         )
         if self.sale_order_line_id and res:
             res['sale_line_ids'] = [(6, 0, [self.sale_order_line_id.id])]