TypeError: Mix.output is not a function error on production

[Senpaiproductions]

I can't seem to get it to work.
Mix.output is undefined and gives an error when i run npm run production

var PrerenderSpaPlugin = require('prerender-spa-plugin');

module.exports.plugins.push(
  new PrerenderSpaPlugin(
    Mix.output().path,
    [ '/' ]
  )
);