Overloading events for hlsjs provider

I am using the hlsjs provider for JW Player (7.12.4), and I need to take some additional action whenever the FRAG_CHANGED event fires. Obviously, I would like to overload it in my own page where I instantiate JW, but I can't figure out how to do it. (I've tried every seeming combination of .on("FRAG_CHANGED") or .on("fragChanged") without success.) For now, I am adding a call directly in the provider.hlsjs.js file, which works perfectly, but that's not an ideal support situation. Is there a way to add a custom JS call cleanly to the hlsjs FRAG_CHANGED event? Thanks.