Reported by Federico Beffa <beffa@ieee.org> at <https://lists.gnu.org/archive/html/guix-devel/2016-05/msg00928.html>. * nix/libstore/local-store.cc (LocalStore::querySubstitutablePaths) (LocalStore::querySubstitutablePathInfos): Return when 'settings.useSubstitutes' is false. * tests/store.scm ("references/substitutes missing reference info"): Make sure to return #f on failure. * tests/store.scm ("substitutable-path-info when substitutes are turned off"): ("substitutable-paths when substitutes are turned off"): New tests.