diff --git a/openwisp_notifications/base/models.py b/openwisp_notifications/base/models.py
index bbcf3793..f0a6c30b 100644
--- a/openwisp_notifications/base/models.py
+++ b/openwisp_notifications/base/models.py
@@ -20,7 +20,7 @@
 from openwisp_notifications import settings as app_settings
 from openwisp_notifications.exceptions import NotificationRenderException
 from openwisp_notifications.types import (
-    NOTIFICATION_CHOICES,
+    get_notification_choices,
     get_notification_configuration,
 )
 from openwisp_notifications.utils import _get_absolute_url, _get_object_link
@@ -31,7 +31,7 @@
 
 class AbstractNotification(UUIDModel, BaseNotification):
     CACHE_KEY_PREFIX = 'ow-notifications-'
-    type = models.CharField(max_length=30, null=True, choices=NOTIFICATION_CHOICES)
+    type = models.CharField(max_length=30, null=True, choices=get_notification_choices)
     _actor = BaseNotification.actor
     _action_object = BaseNotification.action_object
     _target = BaseNotification.target
@@ -212,7 +212,7 @@ class AbstractNotificationSetting(UUIDModel):
     type = models.CharField(
         max_length=30,
         null=True,
-        choices=NOTIFICATION_CHOICES,
+        choices=get_notification_choices,
         verbose_name='Notification Type',
     )
     organization = models.ForeignKey(
diff --git a/openwisp_notifications/tests/test_notification_setting.py b/openwisp_notifications/tests/test_notification_setting.py
index 2bc8c8f4..53d1ed6d 100644
--- a/openwisp_notifications/tests/test_notification_setting.py
+++ b/openwisp_notifications/tests/test_notification_setting.py
@@ -65,7 +65,7 @@ def test_notification_type_registered(self):
 
         self._get_admin()
         self.assertEqual(queryset.count(), 1)
-        self.assertEquals(
+        self.assertEqual(
             queryset.first().__str__(), 'Test Notification Type - default'
         )
 
diff --git a/openwisp_notifications/types.py b/openwisp_notifications/types.py
index 88a5f436..f19f8c3e 100644
--- a/openwisp_notifications/types.py
+++ b/openwisp_notifications/types.py
@@ -23,6 +23,15 @@
 NOTIFICATION_ASSOCIATED_MODELS = set()
 
 
+def get_notification_choices():
+    """
+    Return a list of notification choices.
+    This method used as a callable for 'choices' attribute in models
+    allowing the models to deal with the updated list.
+    """
+    return NOTIFICATION_CHOICES
+
+
 def get_notification_configuration(notification_type):
     if not notification_type:
         return {}