diff --git a/roles/mailman/templates/settings.py.j2 b/roles/mailman/templates/settings.py.j2
index 85849f63cc..37323c1a98 100644
--- a/roles/mailman/templates/settings.py.j2
+++ b/roles/mailman/templates/settings.py.j2
@@ -206,8 +206,11 @@ INSTALLED_APPS = (
 import django
 if django.VERSION[:2] < (1, 6):
     TEST_RUNNER = 'discover_runner.DiscoverRunner'
+else:
+    # Django 1.6 defaults to a JSON serializer, but it won't work with django-openid, see
+    # https://bugs.launchpad.net/django-openid-auth/+bug/1252826
+    SESSION_SERIALIZER = 'django.contrib.sessions.serializers.PickleSerializer'
 
-SESSION_SERIALIZER = 'django.contrib.sessions.serializers.JSONSerializer'
 
 REST_FRAMEWORK = {
     'DEFAULT_RENDERER_CLASSES': (