next issue with safari

-components-header.js

import Link from 'next/link'

const Header = () => (
    <div>
        <Link href='/'>
            <a>Home</a>
        </Link>
        <Link href='/about'>
            <a>About</a>
        </Link>
    </div>
)

export default Header

-pages-about.js

export default () => (
  <div>
    <p>This is the about page</p>
  </div>
)

-pages-index.js

import React, { Component } from 'react'
import fetch from 'unfetch'
import Header from '../components/header'

export default class Index extends Component {

  static async getInitialProps({ req }) {
    if (!req) {
      const nf = await fetch('no-found')
      return nf
    }
    return {}
  }

  render() {
    return (
      <div>
        <Header />
        <p>Hello Next.js</p>
      </div>      
    )
  }

}

next.config.js

module.exports = {

    exportPathMap: () => {
        return {
            '/': { page: '/index'},
            '/about': { page: '/about'}
        }
    }
}

package.json

{
  "name": "next-test",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1",
    "dev": "next",
    "build": "next build && next export"
  },
  "keywords": [],
  "author": "",
  "license": "ISC",
  "dependencies": {
    "next": "^3.0.1-beta.2",
    "react": "^15.6.1",
    "react-dom": "^15.6.1",
    "unfetch": "^2.1.2"
  }
}