diff --git a/jikimo_purchase_request/models/purchase_request.py b/jikimo_purchase_request/models/purchase_request.py
index 3ecd2161..9ed11f13 100644
--- a/jikimo_purchase_request/models/purchase_request.py
+++ b/jikimo_purchase_request/models/purchase_request.py
@@ -114,7 +114,10 @@ class PurchaseRequestLine(models.Model):
 
     def _compute_qty_to_buy(self):
         for pr in self:
-            qty_to_buy = sum(pr.mapped("product_qty")) - sum(pr.mapped("qty_done")) - sum(pr.mapped("qty_in_progress"))
+            qty_to_buy = sum(pr.mapped("product_qty"))
+            if pr.purchase_count > 0:
+                qty_to_buy -= sum(pr.mapped("purchase_lines").filtered(lambda po: po.state != 'cancel').mapped(
+                    "product_qty"))
             pr.qty_to_buy = qty_to_buy > 0.0
             pr.pending_qty_to_receive = qty_to_buy