diff --git a/address.py b/address.py
index 873c0ea08a..3200bc1cf4 100644
--- a/address.py
+++ b/address.py
@@ -1,7 +1,7 @@
 #This file is part of Tryton.  The COPYRIGHT file at the top level of
 #this repository contains the full copyright notices and license terms.
 from trytond.model import Model, fields
-from trytond.pyson import Not, Bool, Eval
+from trytond.pyson import Eval
 import luhn
 
 
@@ -9,7 +9,7 @@ class Address(Model):
     _name = 'party.address'
 
     siret_nic = fields.Char('SIRET NIC', select=1, states={
-            'readonly': Not(Bool(Eval('active'))),
+            'readonly': ~Eval('active', True),
             }, size=5, depends=['active'])
     siret = fields.Function(fields.Char('SIRET'), 'get_siret')
 
diff --git a/party.py b/party.py
index eb2f537f90..d9a34e6dac 100644
--- a/party.py
+++ b/party.py
@@ -1,7 +1,7 @@
 #This file is part of Tryton.  The COPYRIGHT file at the top level of
 #this repository contains the full copyright notices and license terms.
 from trytond.model import Model, fields
-from trytond.pyson import Not, Bool, Eval
+from trytond.pyson import Eval
 import luhn
 
 
@@ -9,7 +9,7 @@ class Party(Model):
     _name = 'party.party'
 
     siren = fields.Char('SIREN', select=1, states={
-            'readonly': Not(Bool(Eval('active'))),
+            'readonly': ~Eval('active', True),
             }, size=9, depends=['active'])
 
     def __init__(self):