TypeError: Class extends value #<Object> is not a constructor or null

Hi there,

can anyone help me to figure out what´s the issue with this error?

I tried to upload a Node.js and Next.js app on Heroku, but it failed because I did not add "type": "module" inside the package.json

After I added "type": "module" to package.json I needed to change the file extension from next.config.js (.js) to next.config.cjs (.cjs (commonJS)). Then I tried to run the app to see if everything works and I got the above error.

It seems that I messed up something with the node.js and the Nextjs environment…

Can anyone help?

Thank you!! :slight_smile:

I made some research and I found this discussion on Next JS Github about the issue I am facing. I tried some of these option but I couldn´t solve the error.

Actually I miss the understanding whats going on under the hood, but maybe someone else can understand it and know a possible solution for this.

If you console.log Document, what is it?

Then what does it do if you change to

import { default as Document, Html, Head, Main, NextScript } from "next/document";


The error I showed in the intro just occured because I changed next.config.js to next.config.cjs after I got this error message:

Then I got this error message:


I think this error message shows up because _document.js is linked to next.config.js and it can not find next.config.cjs. When I delete next.config.cjs I get the same error.

I console.log(Document) inside the console and I get back this:

I still get the same error.

Having the same problem, any updates?

@oAnfibio I split the project in frontend files and backend files and I decided to host the frontend application on Vercel and the backend application on Heroku, then the error no longer appeared. Actually I am not sure if this is neccessary or if there is any another solution to host both frameworks (Next.js and Node.js) within one project and on one hosting platform.

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