How to Fix Three Finger Tap for Firefox

dictionaryfirefox

I used to be able to highlight a word and then tap with three fingers on the trackpad and a dictionary definition would pop up. Sometime in the last month I haven't been able to do that. Firefox has upgraded maybe once or twice and I upgraded to Mac OSX El Captain.

And yes, I did enable it in Preferences:

And it does work in other programs since I enabled it.