Hi list, It appears that the package bundles at CRAN are not stable. The bundle contents can change, and so its hash. I’ve encountered such a problem three times, I think, already, so it’s presumably systemic. The latest (minimal working) example: $ cat manifest.scm (specifications->manifest '("r-foreign")) $ cat channel-specs.scm (list (channel (name 'guix) (url "https://git.savannah.gnu.org/git/guix.git") (commit "d81fb2ae9443994ae5dd1cb5837276fad63f842c"))) $ guix time-machine --commit=d81fb2ae9443994ae5dd1cb5837276fad63f842c --channels=channel-specs.scm -- environment -C --pure --manifest=manifest.scm Updating channel 'guix' from Git repository at 'https://git.savannah.gnu.org/git/guix.git'... building /gnu/store/ixqarfdy375cqwkwgvm9z8cadw87f6gg-foreign_0.8-75.tar.gz.drv... downloading from http://cran.r-project.org/src/contrib/Archive/foreign/foreign_0.8-75.tar.gz... /sha256 hash mismatch for /gnu/store/z6hkz6r1i5cgzjxc5m883lgh1xvjff8s-foreign_0.8-75.tar.gz: expected hash: 0g4mi101srjbl17ydb2hl3854m3xj0llj6861lfr30sp08nkqavl actual hash: 1c888wrn9xf94lp7w9kjw5l8fnarrkv5pi1px5rfnybm1qlysdx5 hash mismatch for store item '/gnu/store/z6hkz6r1i5cgzjxc5m883lgh1xvjff8s-foreign_0.8-75.tar.gz' build of /gnu/store/ixqarfdy375cqwkwgvm9z8cadw87f6gg-foreign_0.8-75.tar.gz.drv failed View build log at '/var/log/guix/drvs/ix/qarfdy375cqwkwgvm9z8cadw87f6gg-foreign_0.8-75.tar.gz.drv.bz2'. cannot build derivation `/gnu/store/vx9187mcdj041sr76bivzbnggr6ajm4q-r-foreign-0.8-75.drv': 1 dependencies couldn't be built guix environment: error: build of `/gnu/store/vx9187mcdj041sr76bivzbnggr6ajm4q-r-foreign-0.8-75.drv' failed I tried . adding another channel with r-foreign redefined in hope that the one in guix would get masked . adding --with-input=r-foreign=r-foreign-redefined (the latter defined in another channel) . adding -L to the environment (also to time-machine) pointing to a directory with r-foreign redefined . an inferior These attempts were either ignored by guix or resulted in guix time-machine: error: got unexpected path `Backtrace:' from substituter Is there a recommended way to deal with such a situation? Thank you for taking a look. WŻ