http-proxy-middleware: accessing 127.0.0.1 instead of localhost, causing ECONNREFUSED

Question

Using webpack2 to compile on the fly an angular application, I configured devServer this way:

proxy: {
    '/api': {
        target: 'http://localhost:52163'
    }
}

The target of the proxy is a IIS Express server. After upgrading from Visual Studio 2012 to 2017, I now get the error ECONNREFUSED when trying to access /api.

I changed http-proxy-middleware to get more information about the error and noticed it tries to connect to 127.0.0.1 instead of localhost.

How can I ensure http-proxy-middleware connects to localhost ?

Thanks