diff --git a/product.py b/product.py
index f54b27487b..ee3eac2ed9 100644
--- a/product.py
+++ b/product.py
@@ -1,13 +1,13 @@
 #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 ModelView, ModelSQL, fields
-from trytond.pyson import Not, Bool, Eval
+from trytond.pyson import Eval
 from trytond.transaction import Transaction
 from trytond.pool import Pool
 
 STATES = {
-    'readonly': Not(Bool(Eval('active'))),
-}
+    'readonly': ~Eval('active', True),
+    }
 DEPENDS = ['active']
 
 
diff --git a/uom.py b/uom.py
index d6980a3948..9d6d957ff4 100644
--- a/uom.py
+++ b/uom.py
@@ -3,13 +3,13 @@
 from decimal import Decimal
 from trytond.model import ModelView, ModelSQL, fields
 from trytond.model.modelstorage import OPERATORS
-from trytond.pyson import Not, Bool, Eval
+from trytond.pyson import Eval
 from trytond.transaction import Transaction
 from trytond.pool import Pool
 
 STATES = {
-    'readonly': Not(Bool(Eval('active'))),
-}
+    'readonly': ~Eval('active', True),
+    }
 DEPENDS = ['active']
 
 class UomCategory(ModelSQL, ModelView):