The GitHub-generated archives Source Code (zip) and Source Code (tar.gz) are incomplete (read more at #156 (comment)). Instead, use v6.2.1.tar.gz. Its SHA256 should be 8ce6ddc8f426a0b828bb5499c6f169f3597380e6cd305189c85576ad2c30b9e5. Or clone this repo at the tag v6.2.1 (and run git archive if you need an archive).