diff --git a/libc/include/utmp.h b/libc/include/utmp.h
index d249f8a..1674491 100644
--- a/libc/include/utmp.h
+++ b/libc/include/utmp.h
@@ -131,6 +131,10 @@
  *
  * Available since API level 23.
  */
+
+#if __BIONIC_AVAILABILITY_GUARD(23)
 int login_tty(int __fd) __INTRODUCED_IN(23);
+#endif /* __BIONIC_AVAILABILITY_GUARD(23) */
+
 
 __END_DECLS