I've just upgraded from Firefox v43.0.1 to v50.1.0. The loss of this irreplaceable extension—the best of its kind—hurts my heart. That said, the endless changes to Firefox have broken so many great extensions, I don't blame any developer for giving up on Firefox. I would too.

The good news is that there's a version of X-notifier for Chrome that works beautifully. I dislike Chrome, but have installed it for the sake of X-notifier.

To the developer, many thanks!