react-router的history问题

Question

import React from 'react';

import {render} from 'react-dom';

import { Router, Route, hashHistory } from 'react-router';

class App extends React.Component {

    render() {

        return (<h1>App</h1>);

    }

}

render((

  <Router history={hashHistory}>

    <Route path="/" component={App}/>

  </Router>

), document.getElementById('root'));

报错信息为

为什么已经引用了hashHistory却还会报错