diff --git a/libc/include/bits/lockf.h b/libc/include/bits/lockf.h
index 195b34a..8f922b9 100644
--- a/libc/include/bits/lockf.h
+++ b/libc/include/bits/lockf.h
@@ -56,6 +56,8 @@
  *
  * See also flock().
  */
+
+#if __BIONIC_AVAILABILITY_GUARD(24)
 int lockf(int __fd, int __op, off_t __length) __RENAME_IF_FILE_OFFSET64(lockf64) __INTRODUCED_IN(24);
 
 /**
@@ -63,5 +65,7 @@
  * even from a 32-bit process without `_FILE_OFFSET_BITS=64`.
  */
 int lockf64(int __fd, int __op, off64_t __length) __INTRODUCED_IN(24);
+#endif /* __BIONIC_AVAILABILITY_GUARD(24) */
+
 
 __END_DECLS