diff --git a/django/contrib/auth/__init__.py b/django/contrib/auth/__init__.py
index 1c821801ef..a0097a01ed 100644
--- a/django/contrib/auth/__init__.py
+++ b/django/contrib/auth/__init__.py
@@ -56,8 +56,14 @@ def logout(request):
     """
     Remove the authenticated user's ID from the request.
     """
-    del request.session[SESSION_KEY]
-    del request.session[BACKEND_SESSION_KEY]
+    try:
+        del request.session[SESSION_KEY]
+    except KeyError:
+        pass
+    try:
+        del request.session[BACKEND_SESSION_KEY]
+    except KeyError:
+        pass
 
 def get_user(request):
     from django.contrib.auth.models import AnonymousUser