diff --git a/models/hr_expense.py b/models/hr_expense.py
index b57e72b2e492a08e7f0a45ab4c79f5322cc7bdce..4bf33ce8a44a975217140de393c7431da1f8c2d0 100644
--- a/models/hr_expense.py
+++ b/models/hr_expense.py
@@ -123,10 +123,12 @@ class CGScopExpense(models.Model):
         """
         Définit le comportement lorsqu'on coche Aller/Retour
         """
-        if self.is_return:
-            self.quantity = self.quantity * 2
-        elif not self.is_return:
-            self.quantity = self.quantity / 2
+        if ((self.product_id.expense_formula == 'fixed_price') and 
+            (self.product_id.is_ik)):
+            if self.is_return:
+                self.quantity = self.quantity * 2
+            elif not self.is_return:
+                self.quantity = self.quantity / 2
 
     # ------------------------------------------------------
     # Button function