Hi, This patch fixes the error that prevents SuperCollider from starting. On Guix 229f4fa9522fb56b014ee9c0d8111e8fb6da764d and after having followed instructions from [0], the behavior is the following: orang3@frastanato ~/code/guix$ guix environment --ad-hoc jack supercollider qjackctl substitute: updating substitutes from 'https://ci.guix.gnu.org'... 100.0% The following derivation will be built: /gnu/store/zzrq8li1plk9ll7yx48lhf27ffk5fvy0-profile.drv The following profile hooks will be built: /gnu/store/jr02fwv31b0a07fcfkalgjjv1bq7ayx8-manual-database.drv /gnu/store/m4zril057cr1m55g7d56q9wp2mrbhhxg-fonts-dir.drv /gnu/store/mrfrb81vzcjxnj321fzi8nqkpvx6s5zw-info-dir.drv /gnu/store/spp41dzc0bmpbr9wvif8r4r2fs02zgfv-ca-certificate-bundle.drv building CA certificate bundle... building fonts directory... building directory of Info manuals... building database for manual pages... building profile with 3 packages... orang3@frastanato ~/code/guix [env]$ sclang SC FFT global init: cosTable initialised. compiling class library... Found 718 primitives. Compiling directory '/gnu/store/rrmvq9gzlvijliwlm35xml65jjqq8s29-supercollider-3.10.4/share/SuperCollider/Extensions' Compiling directory '/home/orang3/.local/share/SuperCollider/Extensions' ERROR: There is a discrepancy. numClassDeps 0 gNumClasses 82 sc3> s.boot Library has not been compiled successfully. The implemented solution is to hardcode SCClassLibrary's path into SuperCollider. [0]: https://guix.gnu.org/manual/en/html_node/Base-Services.html#index-realtime