window is not defined when usring nuxt ssr

vue init nuxt/starter nuxt-vue

yarn

yarn add vue-awesome-swiper -S

nuxt.config.js

module.exports = {
  ...,
  env: {
      browser: true
  },
  plugins: ['~/plugins/vue-awesome-swiper']
}

plugins/vue-awesome-swiper.js

import Vue from 'vue'

if (process.env.browser) {
    const VueAwesomeSwiper = require('vue-awesome-swiper/dist/ssr')
    Vue.use(VueAwesomeSwiper)
}

yarn dev

console printing error message like this: ReferenceError: window is not defined at Object. (nuxt-vue/node_modules/vue-awesome-swiper/dist/ssr.js:18:15)

I see eighteenth lines of vue-awesome-swiper/dist/ssr.js like this var Swiper = window.Swiper || _swiper2.default;