Backbone.js. Router is not a function.

define( ['jquery', 'backbone', 'app/js/views/index'], function($, Backbone, IndexView) {

        var Router = Backbone.Router.extend({
                routes: {
                        "": "index",
                },

                index: function() {
                        var index_view = new IndexView();
                        index_view.render();
                },
        });

        return Router;
});

define(
        [
                'underscore', 'jquery', 'backbone',  '../collections/my', '../routers/router',
        ],
        function (_, $, Backbone, MyCollection, Router) {
        'use strict';
                        
        var IndexView = Backbone.View.extend({
                ...
                render: function () {
                     var router = new Router();
                     router.navigate("projects", {trigger: true});
                }
        });

        return IndexView;