Index: django/contrib/contenttypes/tests.py
===================================================================
--- django/contrib/contenttypes/tests.py	(revision 15796)
+++ django/contrib/contenttypes/tests.py	(working copy)
@@ -59,6 +59,7 @@
             "SERVER_PORT": "80",
         }
         from django.contrib.auth.models import User
+        if not User._meta.installed: return
         user_ct = ContentType.objects.get_for_model(User)
         obj = User.objects.create(username="john")