zoomSnap issue?

Hi, I love this module and it's doing exactly what I need. However I have found a problem that I can't figure out. I can't get 'zoomSnap' to work, it seems to operate as it did on Leaflet before v1.0.0, as if zoomSnap was set to 1.
So at the moment my maps are snapping to single zoom levels but I need fractional ones. As an illustration using Leaflet, running the same code, this is standard leaflet 0.7.2:
http://jsfiddle.net/qjhtue1w/
and this is leaflet 1.0.3 showing the correct level of zoom:
https://jsfiddle.net/1p4jggbf/
leaflet-headless seems to operate like leaflet 0.7.2, but I have checked my dependencies and I'm not using a pre-1.0.0 version of Leaflet.
Any ideas?

Reproduce the issue using the two linked JSFiddle examples, then inspect how leaflet-headless resolves Leaflet and handles the zoomSnap option. Done means fractional zoom levels behave like Leaflet 1.0.3 rather than snapping to whole levels.

Written by the indexing model from the issue text.