[1279] Sass files not found

When using the CSS property in nuxt.conf.js as explained here, trying to load a .scss or .sass file, following error shows in the console:

This relative module was not found:

../assets/main.scss in ./node_modules/babel-loader/lib?{"presets":"vue-app","babelrc":false,"cacheDirectory":true}!./node_modules/vue-loader/lib/selector.js?type=script&index=0!./.nuxt/App.vue

CSS files work as expected.

nuxt.conf.js:

module.exports = { 
  ...
  css: [{
    src: '~assets/main.scss', lang: 'scss'
  }],
  ...
};

Created through vue init nuxt/starter with Nuxt version 1.0.0-rc3.