diff --git a/addons/purchase_requisition/models/purchase.py b/addons/purchase_requisition/models/purchase.py
index 70643757781..6d6a5aebc32 100644
--- a/addons/purchase_requisition/models/purchase.py
+++ b/addons/purchase_requisition/models/purchase.py
@@ -117,12 +117,11 @@ class PurchaseOrderLine(models.Model):
     def _onchange_quantity(self):
         res = super(PurchaseOrderLine, self)._onchange_quantity()
         if self.order_id.requisition_id:
-            for line in self.order_id.requisition_id.line_ids:
-                if line.product_id == self.product_id:
-                    if line.product_uom_id != self.product_uom:
-                        self.price_unit = line.product_uom_id._compute_price(
-                            line.price_unit, self.product_uom)
-                    else:
-                        self.price_unit = line.price_unit
-                    break
+            for line in self.order_id.requisition_id.line_ids.filtered(lambda l: l.product_id == self.product_id):
+                if line.product_uom_id != self.product_uom:
+                    self.price_unit = line.product_uom_id._compute_price(
+                        line.price_unit, self.product_uom)
+                else:
+                    self.price_unit = line.price_unit
+                break
         return res