It was supported immediately for Alpine based images because rustc 1.60+ was available in that distro. Initially when 3.2 was released Debian based images didn

It was supported immediately for Alpine based images because rustc 1.60+ was available in that distro. Initially when 3.2 was released Debian based images didn't support it because Bullseye ships with a version of rustc that's too old to compile YJIT. But https://github.com/docker-library/ruby/commit/6db728e https://github.com/docker-library/ruby/commit/6db728e addressed this a few days ago by installing a pre-compiled version of rustc straight from Rust and YJIT is available in Debian now. You can confirm if it's available to use by running: $ docker container run --rm ruby:3.2.0-slim-bullseye ruby --enable-yjit -v ruby 3.2.0 (2022-12-25 revision a528908271) +YJIT [x86_64-linux] If it weren't available then you would get an unknown argument error.