Hello! Clément Lassieur skribis: > guix substitute: error: download from 'https://mirror.hydra.gnu.org/guix/nar/gzip/9xwrnm3vymsf9w17ayc7dfp5cl1aykq5-metis-5.1.0' failed: 504, "Gateway Time-out" > substitution of /gnu/store/9xwrnm3vymsf9w17ayc7dfp5cl1aykq5-metis-5.1.0 failed The problem is that hydra.gnu.org is currently down¹ and mirror.hydra.gnu.org is just proxying it. What happens here is that is available (cached), whereas the corresponding is not. I don’t have a good solution to this other than temporarily removing mirror.hydra.gnu.org from your substitute URLs. HTH, Ludo’. ¹ https://lists.gnu.org/archive/html/guix-devel/2018-10/msg00434.html