Dynamic segments for route on index in ember

I have an error when I try to get to URL "/posts" in my Ember app. I get a following error:

Uncaught Error: More context objects were passed than there are dynamic segments for the route: posts.index

Which is really puzzling, because there is no dynamic segment for index, my routes look like this:

Router.map(function() {
    this.route('posts', function() {
        this.route('new');
        this.route('show', {
            path: ':post_id'
        });
    });
});

part of the model:

let Post = DS.Model.extend({
    title: DS.attr('string'),
    author: DS.attr('string'),
    content: DS.attr('string')
});

My link which I use to get to /posts:

{{link-to 'Posts' 'posts'}}

Additional info: I am using ember-cli-cordova, so my environment.js contains "defaultLocationType: 'auto'" and I am also using fixtures, so I have a following adapter:

export default DS.FixtureAdapter.extend({
  host: config.apiUrl
});

Does anybody see any problem which would cause the error? Thank you in advance.