loader is failing to load an ES6 module

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?