How To Get Sourcemaps Working For React Css Modules?

I'm trying to setup a React project with react-css-modules, webpack and Hot Module Replacement. Everything is working like a charm but I can't get the CSS sourcemaps to work.

I followed this guide to make HMR work. It involves a BrowserSync setup to update the css file after Webpack writes it to disk.

I use (as suggested by react-css-modules) the ExtractTextPlugin to extract all of the css:

    test: /\.scss$/,
    loader: ExtractTextPlugin.extract('style','css?modules&importLoaders=1&localIdentName=[name]__[local]___[hash:base64:5]!sass')

But if I change this to sourcemaps, as suggested here

loader: ExtractTextPlugin.extract('style', 'css?sourceMap!sass-loader outputStyle=expanded&sourceMap=true&sourceMapContents=true')

I get the error: "root" CSS module is undefined. in my browser console.

You can find my example repo here, but here's the full webpack config I'm using for development.

var webpack = require('webpack');
var path = require('path');
var ExtractTextPlugin = require('extract-text-webpack-plugin');
var WriteFilePlugin = require('write-file-webpack-plugin').default;

module.exports = {
  entry: {
    bundle: [
  devtool: 'cheap-module-source-map',
  debug: true,
  devServer: devServer,
  context: path.resolve(__dirname, './src'),
  output: {
    path: path.resolve(__dirname, './builds'),
    filename: '[name].js',
    publicPath: '/builds/'
  plugins: [
    new webpack.HotModuleReplacementPlugin(),
    new webpack.OldWatchingPlugin(),
    new WriteFilePlugin(),
    new ExtractTextPlugin('[name].css', {
      allChunks: true
  module: {
    loaders: [
        test: /\.js$/,
        loaders: ['react-hot', 'babel-loader'],
        exclude: /node_modules/
        test: /\.scss$/,
        loader: ExtractTextPlugin.extract('style','css?modules&importLoaders=1&localIdentName=[name]__[local]___[hash:base64:5]!sass')
  resolve: {
    extensions: ['', '.js', '.json']

How to make the sourcemap work?



Use this:


i.e. add the sourceMap param to both css & sass loaders. It said so in sass-loader docs.