The GitHub-generated archives Source Code (zip) and Source Code (tar.gz) are incomplete (read more at #156 (comment)). Instead, use v6.0.1.tar.gz. Its SHA256 should be 25e71f222e6464a85aebb0d030e7e9b5881c8803c034fd7143f12f84027c088c. Or clone this repo at the tag v6.0.0 and run git archive yourself.