diff --git a/tests/valuestore.py b/tests/valuestore.py
index 885c00e..3e559ad 100644
--- a/tests/valuestore.py
+++ b/tests/valuestore.py
@@ -267,10 +267,10 @@ class ValuestoreTestCase(object):
                 # check write of too much digits
                 self.assertRaisesRegex(
                     UserError,
-                    r'The number of digits in the value ' +
-                    r'"' + r"'12.345'" +
-                    r'" for field "Value" in "[Book 1 | 10\.00 usd | ' +
-                    r'Open]|balance|12\.35|2" of "Value Store" exceeds ' +
+                    r"The number of digits in the value " +
+                    r'"Decimal\(' +
+                    r"'12\.345'\)" +
+                    r'" for field "Value" in "Value Store" exceeds ' +
                     r'the limit of "2".',
                     ValueStore.write,
                     *[
diff --git a/valuestore.py b/valuestore.py
index 1a4cabf..e6a238d 100644
--- a/valuestore.py
+++ b/valuestore.py
@@ -7,7 +7,7 @@
 from sql.functions import CurrentTimestamp, DateTrunc
 from sql.aggregate import Count
 from sql.conditionals import Coalesce
-from trytond.model import ModelSQL, fields, Unique, Index
+from trytond.model import ModelSQL, fields, Unique
 from trytond.pool import Pool
 from trytond.transaction import Transaction
 from trytond.pyson import Eval, PYSON, PYSONEncoder, PYSONDecoder
@@ -22,7 +22,7 @@ class ValueStore(ModelSQL):
     cashbook = fields.Many2One(
         string='Cashbook', required=True, model_name='cashbook.book',
         ondelete='CASCADE')
-    field_name = fields.Char(string='Field Name', required=True)
+    field_name = fields.Char(string='Field Name', required=True, select=True)
     numvalue = fields.Numeric(
         string='Value', digits=(16, Eval('valuedigits', 6)),
         depends=['valuedigits'])
@@ -39,11 +39,6 @@ class ValueStore(ModelSQL):
                 Unique(t, t.cashbook, t.field_name),
                 'cashbook.msg_value_exists_in_store'),
             ])
-        cls._sql_indexes.update({
-            Index(
-                t,
-                (t.field_name, Index.Equality())),
-            })
 
     def get_rec_name(self, name):
         """ name, balance, state