How to work with multiple targets in webpack proxy?

I have React web app. It had got data from one server (domain). Part of webpack config:

proxy: {
    '/api/**': {
        target: 'https://olddomain.com'
    }
}

Now I have second server. I need to work with both domains something like this:

proxy: {
    '/api/**': {
        target: 'https://olddomain.com'
    },
    '/api/v1/newClass/newMethod': {
        target: 'https://newdomain.com'
    }
}

Please, help me. How to work with multiple targets in webpack proxy?