Users who still want to/have to use the addon (before they find a better solution) may try the following method: go to the bottom of page and click on VERSION INFORMATION then SEE COMPLETE VERSION HISTORY, you'll see a list of previous versions of the Pushbullet addon. Download version 316 instead of 355 (then you have to disable the auto update option of the addon). This method works up to the FF version 52.0 (at the time of writing) .