Comment 3 for bug 1581272

Your description is wrong - systemd happily handles a running gpsd in fireground mode.
Also /etc/default/gpsd is not read by gpsd, but by systemd and the options are passed to gpsd.

Whatever the problem is you are having, your change is not the fix for it.

Please not that gpsd - by default - will not start automatically. Its start is triggered by systemd socket activation. You'll have to add an appropriate systemd config file if you want to change that - for example if you need to have systemd running at system boot.