Disable Kibana Upgrade Assistant (5.6)

I'm looking for a way to disable the upgrade assistant in Kibana 5.6, is that possible?

I don't want my Kibana users to mess with my indices, I was able to deactivate the console but not the assistant.

Thanks

Makes sense. Does xpack.upgrade.enabled: false work for you?

Works great, thanks, you are saving me!

Couldn’t find anything in the documentation though.