fluent-ffmpeg child_process and fs not found

I still getting this error when running npm run hot or npm run watch or npm run dev or whatever on webpack:

These dependencies were not found:

* child_process in ./~/fluent-ffmpeg/lib-cov/utils.js, ./~/fluent-ffmpeg/lib-cov/processor.js and 4 others
* fs in ./~/fluent-ffmpeg/lib-cov/processor.js, ./~/fluent-ffmpeg/lib-cov/capabilities.js and 8 others

I'm a bit confused because if I run npm list I can see both child_process and fs installed.

via Angus Simons