diff --git a/biscuit/apps/alsijil/models.py b/biscuit/apps/alsijil/models.py
index f9fdebadbb36e7e2ab4b612ea1e90d711e43fdc4..4f534302440c931ec4708b2fe9eade452821ba3e 100644
--- a/biscuit/apps/alsijil/models.py
+++ b/biscuit/apps/alsijil/models.py
@@ -48,7 +48,7 @@ class PersonalNoteFilter(SchoolRelated):
     """ A filter definition that can generate statistics on personal note texts. """
 
     identifier = models.CharField(verbose_name=_('Identifier'), max_length=30,
-                                  validators=[lambda v: v.isidentifier()])
+                                  validators=[str.isidentifier])
     description = models.CharField(verbose_name=_('Description'), max_length=60, blank=True)
 
     regex = models.CharField(verbose_name=_('Match expression'), max_length=100)