Hi ng0, I've attached the current version of gnu/packages/rust.scm . For some reason, Rust bootstrap ignores the environment variable AR_x86_64_unknown_linux_gnu even though it doesn't ignore other similar variables (CC_x86_64_unknown_linux_gnu etc). It also ignored config.toml's [target.x86_64-unknown-linux-gnu]. Therefore, the bootstrapping fails when trying to compile the x86_64 version (the i686 version works). To try it, copy the attached file to gnu/packages/rust.scm , overwriting the latter file. Then just invoke $ ./pre-inst-env guix build rustc It will fail like explained above, with the log message: ------------------------------------------------------------------------------------------------------ running: /tmp/guix-build-rustc-1.22.0.drv-0/rustc-1.22.0-src/build/bootstrap/debug/bootstrap build -v finding compilers CC_x86_64-unknown-linux-gnu = "/gnu/store/5sv5zy2kgg6iaqyv8zw49w4243j0xkd0-gcc-5.4.0/bin/gcc" AR_x86_64-unknown-linux-gnu = "/gnu/store/5sv5zy2kgg6iaqyv8zw49w4243j0xkd0-gcc-5.4.0/bin/ar" CC_x86_64-unknown-linux-gnu = "/gnu/store/5sv5zy2kgg6iaqyv8zw49w4243j0xkd0-gcc-5.4.0/bin/gcc" AR_x86_64-unknown-linux-gnu = "/gnu/store/5sv5zy2kgg6iaqyv8zw49w4243j0xkd0-gcc-5.4.0/bin/ar" CC_x86_64-unknown-linux-gnu = "/gnu/store/5sv5zy2kgg6iaqyv8zw49w4243j0xkd0-gcc-5.4.0/bin/gcc" AR_x86_64-unknown-linux-gnu = "/gnu/store/5sv5zy2kgg6iaqyv8zw49w4243j0xkd0-gcc-5.4.0/bin/ar" CXX_x86_64-unknown-linux-gnu = "/gnu/store/5sv5zy2kgg6iaqyv8zw49w4243j0xkd0-gcc-5.4.0/bin/g++" CXX_x86_64-unknown-linux-gnu = "/gnu/store/5sv5zy2kgg6iaqyv8zw49w4243j0xkd0-gcc-5.4.0/bin/g++" running sanity check thread 'main' panicked at ' couldn't find required command: "/gnu/store/5sv5zy2kgg6iaqyv8zw49w4243j0xkd0-gcc-5.4.0/bin/ar" ------------------------------------------------------------------------------------------------------ I've had something similar before - see CFG_LOCAL_RUST_ROOT substitution in rust.scm - but I thought I fixed it. So the next step would have someone find out why it doesn't pick up the value from the environment variable "AR_x86_64_unknown_linux_gnu".