Joomla 3 You can’t remove your own Super User permissions [solved]

On a Joomla! 3 site I got the error “You can’t remove your own Super User permissions.” when trying to save global configuration.

It turned out some previous admin had set the file permissions on this file so the system wasn’t allowed to write to it. I set rw permissions to it using FTP connection to the server and the problem was solved.

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