diff --git a/biscuit/apps/alsijil/models.py b/biscuit/apps/alsijil/models.py
index e2e079d9982b20cbe420346e1d8489f0172e3aef..7c7578f449a5a6036a0b8c3982a6c937c0c5f63f 100644
--- a/biscuit/apps/alsijil/models.py
+++ b/biscuit/apps/alsijil/models.py
@@ -30,7 +30,7 @@ class PersonalNote(models.Model):
                     'lesson_period__period__period', 'person__last_name', 'person__first_name']
 
 
-class LessonDocumentation(models.Model, CRUDMixin):
+class LessonDocumentation(CRUDMixin):
     """ A documentation on a single lesson period. Non-personal, includes
     the topic and homework of the lesson.
     """