Ember adapter unbiddenly changing model name from plural to singular

I have the following Ember adapter for a model called time-zone:

import Ember from 'ember';
import DS from 'ember-data';

export default DS.RESTAdapter.extend({
  namespace: 'api/v2',
  pathForType: function(type) {
    // type here is "time-zone"
    return Ember.String.underscore(type);
  }
});

What I want is for my HTTP request to be sent to /api/v2/time_zones, but it's coming through as /api/v2/time_zone, which is wrong.

This is my model file:

import DS from 'ember-data';

export default DS.Model.extend({
  name: DS.attr('string')
});

And this is the relevant part of my routing file:

import Ember from 'ember';

export default Ember.Route.extend({
  model(params) {
    return Ember.RSVP.hash({
      timeZones: this.store.findAll('time-zone')
    });
  }
});

Adapting a name like timeZone or time-zone to an endpoint URI like /api/v2/time_zones seems like an extremely common use case for Ember, so I'm perplexed at the fact that what I'm trying isn't working.

I can do this and make it work:

    return Ember.String.pluralize(Ember.String.underscore(type));

But that seems like a silly hack for what again must be a super common use case.