--- title: Promise In Next Config --- ## Why This Error Occurred The webpack function in `next.config.js` returned a promise which is not supported in Next.js. For example, below is not supported: ```js filename="next.config.js" module.exports = { webpack: async function (config) { return config }, } ``` ## Possible Ways to Fix It In Next.js versions above `12.0.10`, `module.exports = async () =>` is supported. For older versions, you can check your `next.config.js` for `async` or `return Promise`. Potentially a plugin is returning a `Promise` from the webpack function.