Fixing tabindex issues when using Firefox on a Mac

If you’re conducting an Accessibility check on your site and are having trouble trying to use keyboard controls to tab through pages on Firefox on OSX, the problem is most likely not you.
It can be a head-scratcher when tabindexing through your other browsers goes well but end up at a dead stop in Firefox.
If this is the case for you, it isn’t your site but your OSX keyboard settings.
On your computer, open System Preferences > Keyboard > Shortcuts.

Look to the bottom-left under Keyboard Access and select All controls.
When applying this change, you may need to restart your browser to be able to begin tabbing through pages, although the change seems to activate without restart on Chrome.
Note that this will also enable tabbing through your Bookmarks Bar items as well, so you may notice this when tabbing from your address bar through those items before tabbing continues on pages themselves.
A pretty small tradeoff, really.
Have fun!