diff --git a/mixin.py b/mixin.py
index 973e8b5..a124dc6 100644
--- a/mixin.py
+++ b/mixin.py
@@ -1,9 +1,9 @@
 # -*- coding: utf-8 -*-
-# This file is part of the cashbook-module from m-ds for Tryton.
+# This file is part of the cashbook-module from m-ds.de for Tryton.
 # The COPYRIGHT file at the top level of this repository contains the
 # full copyright notices and license terms.
 
-from trytond.model import ModelView, ModelSQL, fields
+from trytond.model import fields
 from trytond.pyson import Eval, Bool, Or
 from trytond.pool import Pool
 from trytond.modules.currency.ir import rate_decimal
@@ -179,7 +179,7 @@ class SecondCurrencyMixin:
                 if self.currency.id != self.booktransf.currency.id:
                     return self.booktransf.currency.id
 
-    @fields.depends('currency', 'booktransf', '_parent_booktransf.currency')
+    @fields.depends('booktransf', '_parent_booktransf.currency')
     def on_change_with_currency2nd_digits(self, name=None):
         """ currency of transfer-target
         """