Unknown kernel command line option "systemd.journald.storage"

[rmsc]

Aug 15 12:02:25 fedora systemd-journald[411]: Unknown journald kernel command line option "systemd.j
ournald.storage". Ignoring.
Aug 15 12:02:27 fedora systemd-journald[691]: Unknown journald kernel command line option "systemd.j
ournald.storage". Ignoring.

I can't find this key documented anywhere, definitely not working:

ls -ld /run/log/journal/* /var/log/journal/* 2>/dev/null
drwxr-sr-x+ 2 root systemd-journal 60 Aug 15 15:10  /var/log/journal/c9e87d4ab8bd46b3894aa7a6b71fce7c

From the service man page:

Note that journald will initially use volatile storage, until a call to journalctl --flush (or sending SIGUSR1 to journald) will cause it to switch to persistent logging (under the conditions mentioned above). This is done automatically on boot via "systemd-journal-flush.service".

Masking the service instead (systemd.mask=systemd-journal-flush.service) seems to work:

ls -ld /run/log/journal/* /var/log/journal/* 2>/dev/null
drwxr-s---+ 2 root systemd-journal 60 Aug 15 15:16  /run/log/journal/729dc92cfcb24f7fbb97e62e36b413f0
drwxr-s---+ 2 root systemd-journal 60 Aug 15 15:16  /run/log/journal/7361bf14c1394bcb95c86292e78dfcf7