Hi, Using Guix 55685e4, I get: --8<---------------cut here---------------start------------->8--- $ guix build -S --no-substitutes gprolog The following derivation will be built: /gnu/store/yjrcalnckwmi1ah217xh85sd7ksjcxfw-gprolog-1.4.5.tar.gz.drv building /gnu/store/yjrcalnckwmi1ah217xh85sd7ksjcxfw-gprolog-1.4.5.tar.gz.drv... Starting download of /gnu/store/wm72f18w1gvshkz39yp12vnmnkkib79k-gprolog-1.4.5.tar.gz From http://gprolog.org/gprolog-1.4.5.tar.gz... downloading from http://gprolog.org/gprolog-1.4.5.tar.gz ... gprolog-1.4.5.tar.gz 3.4MiB 50.1MiB/s 00:00 [##################] 100.0% sha256 hash mismatch for /gnu/store/wm72f18w1gvshkz39yp12vnmnkkib79k-gprolog-1.4.5.tar.gz: expected hash: 0z4cc42n3k6i35b8mr816iwsvrpxshw6d7dgz6s2h1hy0l7g1p5z actual hash: 18mrmx44fll0g1qphadna9g6m7miw8d22lkjavah22vzc38kalyf hash mismatch for store item '/gnu/store/wm72f18w1gvshkz39yp12vnmnkkib79k-gprolog-1.4.5.tar.gz' build of /gnu/store/yjrcalnckwmi1ah217xh85sd7ksjcxfw-gprolog-1.4.5.tar.gz.drv failed View build log at '/var/log/guix/drvs/yj/rcalnckwmi1ah217xh85sd7ksjcxfw-gprolog-1.4.5.tar.gz.drv.bz2'. guix build: error: build of `/gnu/store/yjrcalnckwmi1ah217xh85sd7ksjcxfw-gprolog-1.4.5.tar.gz.drv' failed $ guix build -S gprolog substitute: updating substitutes from 'https://ci.guix.gnu.org'... 100.0% 3.6 MB will be downloaded: /gnu/store/wm72f18w1gvshkz39yp12vnmnkkib79k-gprolog-1.4.5.tar.gz substituting /gnu/store/wm72f18w1gvshkz39yp12vnmnkkib79k-gprolog-1.4.5.tar.gz... downloading from https://ci.guix.gnu.org/nar/wm72f18w1gvshkz39yp12vnmnkkib79k-gprolog-1.4.5.tar.gz ... gprolog-1.4.5.tar.gz 3.4MiB 5.9MiB/s 00:01 [##################] 100.0% /gnu/store/wm72f18w1gvshkz39yp12vnmnkkib79k-gprolog-1.4.5.tar.gz --8<---------------cut here---------------end--------------->8--- It is probably an upstream in-place replacement. This kind of thing is really annoying because it means that people using substitutes do not notice whereas people building from source do. All the best, simon