https://crystal-lang.org/2021/03/22/crystal-1.0-what-to-expect.html It does emerge by renaming the old ebuild into my local repo, but I don't know with patch associated with USE blocking-stdio-hack: --- # emerge -1p dev-lang/crystal These are the packages that would be merged, in order: Calculating dependencies ... done! [ebuild R ] dev-lang/crystal-1.0.0::local USE="-blocking-stdio-hack -debug doc examples xml yaml" 0 KiB -