diff --git a/docs/topics/auth/customizing.txt b/docs/topics/auth/customizing.txt
index 7c17d26b47..8997d6c24d 100644
--- a/docs/topics/auth/customizing.txt
+++ b/docs/topics/auth/customizing.txt
@@ -398,8 +398,9 @@ the :setting:`AUTH_USER_MODEL` setting that references a custom model::
 
      AUTH_USER_MODEL = 'myapp.MyUser'
 
-This dotted pair describes the name of the Django app, and the name of the Django
-model that you wish to use as your User model.
+This dotted pair describes the name of the Django app (which must be in your
+:setting:`INSTALLED_APPS`), and the name of the Django model that you wish to
+use as your User model.
 
 .. admonition:: Warning