Ember route model return through promise

I have a fixture:

App.QuerySequence.FIXTURES = [
    {
        id: '1',
        sequence: 'ATTAGAC'
    }
];

which I am giving through index route:

App.IndexRoute = Ember.Route.extend({
    model: function () {
        return this.store.find('querySequence', '1');
    }
});

and this one works. But I first need to process data of sequence. So I tried using:

App.IndexRoute = Ember.Route.extend({
    model: function () {
        return {
            query: this.store.find('querySequence', '1'),
            words: this.store.find('querySequence', '1').then(function(query) {
                return getWords(query.get('sequence'), 4);
            })
        };
    }
});

...

function getWords(sequence, wordSize) {
    console.log(sequence);
    var words = [];
    for (var i = 0; i < sequence.length - wordSize; i++) {
        words.pushObject(sequence.substr(i, wordSize));
    }
    return words;
}

With :

<script type="text/x-handlebars" id="index">
    <!--test view-->
    <label>Query: </label><span>{{query.sequence}}</span><br/>
    <label>Query words:</label><br/>
    <ul>
    {{#each word in words}}
        <li>{{word}}</li>
    {{else}}
        <li>Loading...</li>
    {{/each}}
    </ul>
</script>

Which ends up with error : Error: Assertion Failed: The value that #each loops over must be an Array. You passed {_id: 49, _label: undefined, _state: undefined, _result: undefined, _subscribers: }.

I know that getWords isn't called (also everything works with words: getWords('ACTGACCCATGAACATA', 4),). Without returning words from model app doesn't generate any error.

What am I doing wrong? I've spend hours trying to google my problem, but maybe due to fact, that I'm a total beginner, I couldn't find anything.