diff --git a/django/contrib/auth/middleware.py b/django/contrib/auth/middleware.py
index ae7d868134..4b3ed54960 100644
--- a/django/contrib/auth/middleware.py
+++ b/django/contrib/auth/middleware.py
@@ -14,7 +14,6 @@ class LazyUser(object):
 
 class AuthenticationMiddleware:
     def process_request(self, request):
-        from django.contrib.auth.models import SESSION_KEY
         assert hasattr(request, 'session'), "The Django authentication middleware requires session middleware to be installed. Edit your MIDDLEWARE_CLASSES setting to insert 'django.contrib.sessions.middleware.SessionMiddleware'."
         request.__class__.user = LazyUser()
         return None