diff --git a/libc/include/semaphore.h b/libc/include/semaphore.h
index 6ad9ea3..9c4702d 100644
--- a/libc/include/semaphore.h
+++ b/libc/include/semaphore.h
@@ -45,7 +45,11 @@
 
 #define SEM_FAILED __BIONIC_CAST(reinterpret_cast, sem_t*, 0)
 
+
+#if __BIONIC_AVAILABILITY_GUARD(30)
 int sem_clockwait(sem_t* _Nonnull __sem, clockid_t __clock, const struct timespec* _Nonnull __ts) __INTRODUCED_IN(30);
+#endif /* __BIONIC_AVAILABILITY_GUARD(30) */
+
 int sem_destroy(sem_t* _Nonnull __sem);
 int sem_getvalue(sem_t* _Nonnull __sem, int* _Nonnull __value);
 int sem_init(sem_t* _Nonnull __sem, int __shared, unsigned int __value);
@@ -59,7 +63,11 @@
  * Note that sem_clockwait() allows specifying an arbitrary clock and has superseded this
  * function.
  */
+
+#if __BIONIC_AVAILABILITY_GUARD(28)
 int sem_timedwait_monotonic_np(sem_t* _Nonnull __sem, const struct timespec* _Nonnull __ts) __INTRODUCED_IN(28);
+#endif /* __BIONIC_AVAILABILITY_GUARD(28) */
+
 int sem_trywait(sem_t* _Nonnull __sem);
 int sem_wait(sem_t* _Nonnull __sem);