Build fails when bundling css, Error: "extract-text-webpack-plugin" loader is used without the corresponding plugin

[au-re]

I get the following error when running react-app-rewired build --library:

/src/components/Button/Button.css
Module build failed: Error: "extract-text-webpack-plugin" loader is used without the corresponding plugin, refer to https://github.com/webpack/extract-text-webpack-plugin for the usage example

The css is imported as: import "./Button.css".

Replacing

config.plugins=[ ]

with

config.plugins = [
 new ExtractTextPlugin("styles.css"),
];

seems to solve the problem..