};
      useSubstitutes = mkOption {
        type = types.bool;
        default = false;
        description = ''
          Whether to use binary caches for downloading store paths. Note that
          binary substitutions trigger (a potentially large number of) additional
          HTTP requests that slow down the queue monitor thread significantly.
          Also, this Hydra instance will serve those downloaded store paths to
          its users with its own signature attached as if it had built them
          itself, so don't enable this feature unless your active binary caches
          are absolute trustworthy.
        '';

          { ExecStart = "@${cfg.package}/bin/hydra-queue-runner hydra-queue-runner -v --option build-use-substitutes false";

          { ExecStart = "@${cfg.package}/bin/hydra-queue-runner hydra-queue-runner -v --option build-use-substitutes ${if optionalString cfg.useSubstitutes then "true" else "false"}";