Resolving background-image URLs in CSS files for Webpack

I know this probably gets asked often, but I've looked at several similar questions, but can't quite figure out how to resolve URLs in this scenario.

Note: I am NOT using a dev server or any special framework; just Webpack and opening files through the browser (file://). The Webpack-built files must work without a server, so please do not suggest using one. Also, I'm using Webpack 3.

File structure:

src/
- assets/
  - img/
    - backgrounds/
      - some-bg.jpg
  - css/
    - layouts.css
- index.html
- main.js
node_modules/
webpack.conf.js

layouts.css references some-bg.jpg as a background image:

body {
    background-image: url('../img/backgrounds/some-bg.jpg');
}

In my Webpack config, I have:

module.exports = {
    entry: './src/main.js',
    output: {
        path: path.resolve(__dirname, "dist"),
        filename: 'bundle.js'
    },
     module: {
         loaders: [
           {
                test: /\.css$/,
                use: ExtractTextPlugin.extract({
                    use: "css-loader",
                    fallback: "style-loader"
                })
           },
           {
                test: /\.(jpe?g|png|gif)$/,
                use: {
                    loader: 'url-loader',
                    options: {
                        limit: 8192,
                        name: "./assets/img/[name].[ext]"
                    }
                }
           }
        ]
    }
    plugins: [
        new ExtractTextPlugin({
            filename: "./assets/css/style.css"
        }),
    ]
// ...
}

All of the images referenced in index.html are correctly changed to ./assets/img/whatever.png.

However, the background-image url is changed to url(./assets/img/some-bg.jpg), which points to the path dist/assets/css/assets/img/some-bg.jpg.

What do I have to change to get the url to simply be dist/assets/img/some-bg.jpg?

Finally got it working. With this specific structure, I had to specify a publicPath on the ExtractTextPlugin (even though I did not have a regular publicPath set for Webpack itself).

{
  test: /\.css$/,
  use: ExtractTextPlugin.extract({
    use: "css-loader",
    fallback: "style-loader",
    publicPath: "../../"
  })
},