Group-By Bug (Unable to set key with some symbols)

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName: 'Ember Twiddle'
});

models.contract.js

import Model from "ember-data/model";
import attr from "ember-data/attr";

export default Model.extend({
  title: attr('string'),
  supplierName: attr('string'),
});

routes.index.js

import Ember from 'ember';

export default Ember.Route.extend({
  model() {
    return this.store.push({
      data: [
        {
          id: '1',
          type: 'contract',
          attributes: {
            title: 'Master Agreement',
            supplierName: 'Fusible LLC'
          }
        },
        {
          id: '2',
          type: 'contract',
          attributes: {
            title: 'Services Agreement',
            supplierName: 'Betacone Data Inc'
          }
        },
        {
          id: '3',
          type: 'contract',
          attributes: {
            title: 'Client Agreement',
            supplierName: 'Betacone Data Inc'
          }
        },
        // The bug is caused by the periods in the supplierName. Remove
        // them to get this example to render properly.
        {
          id: '4',
          type: 'contract',
          attributes: {
            title: 'User Agreement',
            supplierName: 'Yamazaki Hinoki K.K.'
          }
        }
      ]
    });
  }
});

templates.application.hbs

<h3>Ember Composable Helpers <br>
Group-By Bug</h3>

{{outlet}}

templates.index.hbs

{{#each-in (group-by "supplierName" model) as |supplierName contracts|}}
  <h5>{{supplierName}} Contracts</h5>
  
  <ul>
    {{#each contracts as |contract|}}
      <li>{{contract.title}}</li>
    {{/each}}
  </ul>
{{/each-in}}

twiddle.json

{
  "version": "0.10.4",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "2.6.0",
    "ember-data": "2.6.0",
    "ember-template-compiler": "2.6.0"
  },
  "addons": {
  	"ember-composable-helpers": "1.1.1"
  }
}