This error (_0_0. call$1 is not a function) frequently arises from problems with Webpack and styles following significant updates. Make sure to verify the compatibility of your SASS-related packages with Next. js 15 when using SCSS modules.

Update sass and sass-loader to their latest versions by executing:

npm install sass@latest sass-loader@latest

After that, remove any cache by deleting. next and node_modules directories, and proceed to reinstall the dependencies using npm install. If you have custom Webpack configurations in your next. config. js file, try temporarily commenting them out and rebuilding the project to check if they are causing compatibility issues. If this guidance proves helpful, re-enable configurations one by one to pinpoint the issue.

You might want to consider reverting CSS-related dependencies (such as sass or postcss-loader) to their previous versions if recent updates have caused conflicts. You have the option to utilize npx npm-check-updates to identify any version discrepancies.

For the final test, you can disable CSS modules by simply renaming file. module. scss to file. scss and importing it globally in _app. tsx. If the problem is solved, it probably indicates a conflict in handling CSS modules. You may want to consider going back to Next. js 15. 0. 1 as an option to investigate any possible issues with the current version.