loader is failing to load an ES6 module

[stevesims]

In my project we're using moment-range, which got an update in it's version 3 to be an ES6 module.

Previously we'd been loading it using ember-browserify and thus were doing import DateRange from 'npm:moment-range'. This doesn't work with the updated version, as one will get the error TypeError: _npmMomentRange.default is not a constructor, presumably as there's no default export on the module. Besides, as it's an ES6 module from what I understand the npm: prefix shouldn't be necessary.

Omitting the npm: prefix however gives a different error:
Error: Could not find module 'moment-range' imported from 'foo/bar/baz'
which is thrown by the missingModule function in loader.js. Poking about a bit, there's no sign of moment-range in the registry inside loader.js.

I may well be doing something wrong, but I'm at a loss to see what I should be doing differently.

Any suggestions?