diff --git a/src/helper/slbt_dump_machine.c b/src/helper/slbt_dump_machine.c
index 1357509..3e0c65d 100644
--- a/src/helper/slbt_dump_machine.c
+++ b/src/helper/slbt_dump_machine.c
@@ -56,7 +56,7 @@ int slbt_dump_machine(
 	char	program[PATH_MAX];
 
 	/* setup */
-	if (!machine || !--buflen) {
+	if (!machine || !buflen || !--buflen) {
 		errno = EINVAL;
 		return -1;
 	}