Unable to enable MokListTrusted (--trust-mok)

[jodab]

Running mokutil --trust-mok and setting a password for verification works fine. Upon reboot it tries to set the MokListTrusted efivar but then responds with "Failed to delete MokListTrusted state".

I've tried with Secure Boot enabled as well as disabled, and in setup mode, but the result is the same.

Where do I go from here?