webpack-dev-server: Can't get hot reload to work with my setup...

I’m using the following webpack and webpack-dev-server versions:

"webpack": "^2.2.0-rc.7",
"webpack-dev-server": "^2.2.0-rc.0"

And this is my webpack.config.js file:

var path = require('path');

var HtmlWebpackPlugin = require('html-webpack-plugin');

module.exports = {
    entry: {
        app: path.join(__dirname, 'app', 'src', 'Index.tsx')
    },

    output: {
        path: path.join(__dirname, 'build'),
        filename: '[name].[hash:8].js'
    },

    devtool: 'source-map',

    resolve: {
        extensions: ['.ts', '.tsx', '.js']
    },

    module: {
        rules: [
            {
                include: path.join(__dirname, 'app'),
                loader: 'awesome-typescript-loader',
                test: /\.tsx?$/,
            },
            {
                include: path.join(__dirname, 'app'),
                loader: 'source-map-loader',
                test: /\.js$/,
                enforce: 'pre'
            }
        ]
    },

    plugins: [
        new HtmlWebpackPlugin({
            template: path.join(__dirname, 'app', 'index.html'),
            favicon: path.join(__dirname, 'app', 'favicon.ico'),
            inject: 'body',
        })
    ],

    externals: {
        'react': 'React',
        'react-dom': 'ReactDOM'
    }
};

In case it’s not obvious, I’m using TypeScript (not sure how relevant that is):

"awesome-typescript-loader": "^3.0.0-beta.18",
"typescript": "^2.1.5",

I also have an NPM script to launch the server (npm run server):

"scripts": {
    "server": "./node_modules/.bin/webpack-dev-server --hot",
}

My app is currently very simple… I have the main React page (Index.tsx) which renders 2 components (CompA.tsx and CompB.tsx). When I change CompB, I expect the page to NOT full reload and instead just that component to reload. Is that what HMR is supposed to do, correct?

But there’s what I get when I change CompB.tsx:

I know there’s a recent issue (#741) about a similar problem and I looked into the suggested link (http://andrewhfarmer.com/webpack-hmr-tutorial/) but didn’t help. Since I’m using beta versions and TypeScript and those might have some impact on my exact problem, I decided to create a new issue. Hope it’s ok…

Any idea what am I doing wrong?