export default {
  entry: './index.js',
   plugins: [
    stylelint({
        include: ["./**/*.{css}"],
    }),
      postcss({
        extract: false,
        inject: true,
        plugins: [cssUrl({url: "inline"})],
        minimize: isProduction,
        modules: true,
        sourceMap: isProduction ? "inline" : ""
      }),
  ]
},

When postcss minimize option is set to true the following fatal error occurs:

[!] (plugin postcss) TypeError: Cannot read property 'syntax' of undefined
components/SliderVertical/Slider.css
TypeError: Cannot read property 'syntax' of undefined
at Declaration.toString (/home/me/test/node_modules/postcss-syntax/patch-postcss.js:38:67)
at String ()