diff --git a/src/collective/contact/core/content/directory.py b/src/collective/contact/core/content/directory.py
index 2248c93..da0479e 100644
--- a/src/collective/contact/core/content/directory.py
+++ b/src/collective/contact/core/content/directory.py
@@ -13,14 +13,16 @@
 from zope.interface import Interface
 
 
+def is_valid_identifier(identifier):
+    idnormalizer = getUtility(IIDNormalizer)
+    return idnormalizer.normalize(identifier) == identifier
+
+
 class INameTokenTableRowSchema(Interface):
     """Schema for dict rows used in DataGridFields
     name is the 'real' name
     token is the token used in the vocabularies
     """
-    def is_valid_identifier(identifier):
-        idnormalizer = getUtility(IIDNormalizer)
-        return idnormalizer.normalize(identifier) == identifier
 
     name = schema.TextLine(title=_(u"Name"))
     token = schema.TextLine(title=_(u"Token"), constraint=is_valid_identifier)
diff --git a/src/collective/contact/core/tests/test_content_types.py b/src/collective/contact/core/tests/test_content_types.py
index caf39d8..644a3c6 100644
--- a/src/collective/contact/core/tests/test_content_types.py
+++ b/src/collective/contact/core/tests/test_content_types.py
@@ -1,5 +1,6 @@
 # -*- coding: utf8 -*-
 
+from collective.contact.core.content.directory import is_valid_identifier
 from collective.contact.core.interfaces import IContactCoreParameters
 from collective.contact.core.testing import INTEGRATION
 from ecreall.helpers.testing.base import BaseTest
@@ -51,6 +52,16 @@ def test_directory(self):
         self.assertIn({'name': 'Regiment', 'token': 'regiment'},
                       mydirectory.organization_levels)
 
+    def test_is_valid_identifier(self):
+        self.assertFalse(is_valid_identifier('Toto'))
+        self.assertTrue(is_valid_identifier('toto'))
+        self.assertTrue(is_valid_identifier('toto56'))
+        self.assertFalse(is_valid_identifier('toto 56'))
+        self.assertTrue(is_valid_identifier('toto-56'))
+        self.assertFalse(is_valid_identifier('toto-56@'))
+        self.assertFalse(is_valid_identifier('toto-56à'))
+        self.assertFalse(is_valid_identifier('toto-56É'))
+
 
 class TestPerson(TestContentTypes):