diff --git a/plinth/notification.py b/plinth/notification.py
index 89140b86e..26c9c5858 100644
--- a/plinth/notification.py
+++ b/plinth/notification.py
@@ -70,7 +70,9 @@ class Notification(models.StoredNotification):
     following fields are present in the model:
 
     'id' is a unique string identifier for the notification and acts as the
-    primary key for the stored database table.
+    primary key for the stored database table. Only the following chars are
+    currently allowed: A-Z, a-z, 0-9, - and =. If other chars must be used, it
+    is recommended to use base32 encoding.
 
     'app_id' is the unique ID of the app showing the notification.
 
@@ -154,6 +156,7 @@ class Notification(models.StoredNotification):
     been dismissed by the user.
 
     """
+
     class Meta:  # pylint: disable=too-few-public-methods
         """Meta properties of the Notification model."""
         proxy = True
diff --git a/plinth/urls.py b/plinth/urls.py
index 8d69881ed..5317ef32c 100644
--- a/plinth/urls.py
+++ b/plinth/urls.py
@@ -32,6 +32,6 @@ urlpatterns = [
     url(r'locked/$', public(CaptchaLoginView.as_view()), name='locked_out'),
 
     # Notifications
-    url(r'^notification/(?P<id>[a-z0-9-]+)/dismiss/$',
+    url(r'^notification/(?P<id>[A-Za-z0-9-=]+)/dismiss/$',
         views.notification_dismiss, name='notification_dismiss')
 ]