diff --git a/modules/purchase_trade/fee.py b/modules/purchase_trade/fee.py
index 685993a..2521bf5 100755
--- a/modules/purchase_trade/fee.py
+++ b/modules/purchase_trade/fee.py
@@ -172,12 +172,13 @@ class Fee(ModelSQL,ModelView):
         return 'pay'
 
     def get_unit(self, name=None):
-        Lot = Pool().get('lot.lot')
-        if self.lots:
-            if self.lots[0].line:
-                return self.lots[0].line.unit
-            if self.lots[0].sale_line:
-                return self.lots[0].sale_line.unit
+        FeeLots = Pool().get('fee.lots')
+        fl = FeeLots.search(['fee','=',self.id])
+        if fl:
+            if fl[0].lot.line:
+                return fl[0].lot.line.unit
+            if fl[0].lot.sale_line:
+                return fl[0].lot.sale_line.unit
 
     @classmethod
     @ModelView.button