diff --git a/sf_manufacturing/models/mrp_production.py b/sf_manufacturing/models/mrp_production.py
index 3269164c..6584b04f 100644
--- a/sf_manufacturing/models/mrp_production.py
+++ b/sf_manufacturing/models/mrp_production.py
@@ -38,7 +38,7 @@ class MrpProduction(models.Model):
     def _compute_deadline_of_delivery(self):
         for production in self:
             sale_order_ids = production.procurement_group_id.mrp_production_ids.move_dest_ids.group_id.sale_id.ids
-            if len(sale_order_ids) < 1:
+            if not sale_order_ids or len(sale_order_ids) < 1:
                 continue
             sale_id = self.env['sale.order'].sudo().browse(sale_order_ids[0])
             if sale_id: