Bug: https://bugs.gentoo.org/895986
--- a/galaxis.c
+++ b/galaxis.c
@@ -6,6 +6,7 @@
  * SPDX-License-Identifier: BSD-2-Clause
  */
 #define _POSIX_SOURCE
+#define _GNU_SOURCE
 
 #include <stdio.h>
 #include <termios.h>