diff --git a/modules/purchase_trade/fee.py b/modules/purchase_trade/fee.py
index 77829cd..563c459 100755
--- a/modules/purchase_trade/fee.py
+++ b/modules/purchase_trade/fee.py
@@ -111,6 +111,7 @@ class Fee(ModelSQL,ModelView):
         if lqt:
             return lqt[0].id 
     
+    @fields.depends('mode','unit')
     def on_change_with_packing_category(self, name=None):
         UnitCategory = Pool().get('product.uom.category')
         packing = UnitCategory.search(['name','=','Packing'])