diff --git a/product/ERP5/Document/DeliveryLine.py b/product/ERP5/Document/DeliveryLine.py
index d178249d22e04fc550c0c5ed9fbef980ba70b2a0..b0a9b79e42f6a4740fed4123b2a7bc76557859de 100755
--- a/product/ERP5/Document/DeliveryLine.py
+++ b/product/ERP5/Document/DeliveryLine.py
@@ -211,7 +211,9 @@ Une ligne tarifaire."""
 
     def _getTargetTotalPrice(self, context):
       if not self.hasCellContent():
-        return self.getTargetQuantity() * self.getPrice(context=context)
+        target_quantity = self.getTargetQuantity() or 0.0
+        price = self.getPrice(context=context) or 0.0
+        return target_quantity * price
       else:
         # Use MySQL
         aggregate = self.DeliveryLine_zGetTotal()[0]