diff --git a/modules/purchase_trade/fee.py b/modules/purchase_trade/fee.py
index 2521bf5..b605db0 100755
--- a/modules/purchase_trade/fee.py
+++ b/modules/purchase_trade/fee.py
@@ -93,10 +93,18 @@ class Fee(ModelSQL,ModelView):
         ('brut', 'Gross'),
         ], string='W. type')
 
-    @fields.depends('mode')
+    @fields.depends('mode','_parent_line.lots','_parent_sale_line.lots')
     def on_change_with_unit(self, name=None):
         if self.mode != 'ppack':
-            return self.get_unit()
+            line = self.line
+            if not line:
+                line = self.sale_line
+            if line:
+                if line.lots:
+                    if len(line.lots) == 1:
+                        return line.lots[0].lot_unit_line
+                    else:
+                        return line.lots[1].lot_unit_line
         else:
             return self.unit