diff --git a/modules/purchase_trade/fee.py b/modules/purchase_trade/fee.py
index 5d451e2..33a787c 100755
--- a/modules/purchase_trade/fee.py
+++ b/modules/purchase_trade/fee.py
@@ -66,7 +66,7 @@ class Fee(ModelSQL,ModelView):
     quantity = fields.Numeric("Qt",digits='unit',states={'readonly': (Eval('mode') != 'ppack') | Bool(Eval('auto_calculation'))})
     unit = fields.Many2One('product.uom',"Unit",domain=[
             If(Eval('mode') == 'ppack',
-                ('category', '=', 8),
+                ('category', '=', Eval('packing_category')),
                 ()),
             ],
         states={
@@ -114,7 +114,7 @@ class Fee(ModelSQL,ModelView):
         UnitCategory = Pool().get('product.uom.category')
         packing = UnitCategory.search(['name','=','Packing'])
         if packing:
-            return packing[0].id
+            return packing[0]
 
     @fields.depends('line','sale_line','shipment_in','lots','price','unit','auto_calculation','mode','_parent_line.unit','_parent_line.lots','_parent_sale_line.unit','_parent_sale_line.lots')
     def on_change_with_quantity(self, name=None):