Requirejs + Backbone Uncaught TypeError: Cannot read property 'each' of undefined

The error points to the backbone.js:219 library. The error is thrown in my main.js file in the require(['app'], function.

main.js file:

require.config({
  baseUrl: 'scripts',

  paths: {
    app: '../app',
    jquery: 'jquery',
    underscore: 'underscore',
    backbone: 'backbone',
    router: '../router'
  },

  shim: {
        backbone: {
            deps: ['jquery','underscore'],
            exports: 'Backbone'
        }
    }
});

require(['app'], function (App) {
    App.initialize();
});

My app.js file:

define([
  'jquery',
  'underscore',
  'backbone',
  'router' // Request router.js
], function($, _, Backbone, Router){

  var initialize = function(){
    // Pass in our Router module and call it's initialize function
    Router.initialize();
  };

  return {
    initialize: initialize
  };
});

My router.js file:

require(['jquery', 'underscore', 'backbone'], function ($, _, Backbone) {
  'use strict';

// Router
  var AppRouter = Backbone.Router.extend({

    routes:{
      "":"list",
      "wines/:id":"wineDetails"
    },

    list:function () {
      this.wineList = new WineCollection();
      this.wineListView = new WineListView({model:this.wineList});
      this.wineList.fetch();
      $('#sidebar').html(this.wineListView.render().el);
    },

    wineDetails:function (id) {
      this.wine = this.wineList.get(id);
      this.wineView = new WineView({model:this.wine});
      $('#content').html(this.wineView.render().el);
    }
  });

  return AppRouter;
});

This question seems to similar to this one, but none of the suggestions worked for me.