Error while processing route: todos undefined is not a function

I'm getting this error after the Displaying Model Data step while trying to follow the TodoMVC demo app on the Ember site (http://guides.emberjs.com/v1.10.0/getting-started/). My javascript code up to this point is:

window.Todos = Ember.Application.create();

Todos.ApplicationAdapter = DS.FixtureAdapter.extend();

Todos.Router.map(function () {
    this.resource('todos', { path: '/' });
});

Todos.TodosRoute = Ember.Route.extend({
    model: function () {
        return this.store.find('todo');
    }
});

Todos.Todo = DS.Model.extend({
    title: DS.attr('string'),
    isCompleted: DS.attr('boolean')
});

Todos.Todo.FIXTURES = [
{
    id: 1,
    title: 'Learn Ember.js',
    isCompleted: true
},
{
    id: 2,
    title: '...',
    isCompleted: false
},
{
    id: 3,
    title: 'Profit!',
    isCompleted: false
}
];