Sometimes `process.cwd()` returns path with a small drive letter, like `d:\` And this regex `!/^[A-Z]:\\$/.test(cwdDrive)` is failed to match it. Possible solution is to use this regex `!/^[A-Za-z]:\\$/.test(cwdDrive)` https://github.com/madyankin/postcss-modules/blob/55b09950d76140ddef25fd60f4fd788b773f8e70/src/css-loader-core/loader.js#L49