Env variables are undefined when deploying

[milorue]

I have a Next.js application that I'm trying to deploy and its become a nightmare for me. I'm storing my env variables in a next.config.js in this format:

module.exports = {
    env: {
        KEY: 'akey',
        SECONDKEY: 'asecondkey',
},
}

When I run npm run build and npm start it works fine locally but my variables are undefined when deploying to Vercel with their environmental variables inputs. When accessing the variables in _app.js i'm using process.env.KEY but it comes up as undefined.

Any help would be greatly appreciated