diff --git a/libc/include/pthread.h b/libc/include/pthread.h
index a0fcc88..f1085a8 100644
--- a/libc/include/pthread.h
+++ b/libc/include/pthread.h
@@ -133,7 +133,7 @@
 
 __BEGIN_DECLS
 
-int pthread_atfork(void (*)(void), void (*)(void), void(*)(void));
+int pthread_atfork(void (*)(void), void (*)(void), void (*)(void)) __INTRODUCED_IN(21);
 
 int pthread_attr_destroy(pthread_attr_t*) __nonnull((1));
 int pthread_attr_getdetachstate(const pthread_attr_t*, int*) __nonnull((1, 2));
@@ -153,10 +153,11 @@
 int pthread_attr_setstacksize(pthread_attr_t*, size_t) __nonnull((1));
 
 int pthread_condattr_destroy(pthread_condattr_t*) __nonnull((1));
-int pthread_condattr_getclock(const pthread_condattr_t*, clockid_t*) __nonnull((1, 2));
+int pthread_condattr_getclock(const pthread_condattr_t*, clockid_t*) __nonnull((1, 2))
+  __INTRODUCED_IN(21);
 int pthread_condattr_getpshared(const pthread_condattr_t*, int*) __nonnull((1, 2));
 int pthread_condattr_init(pthread_condattr_t*) __nonnull((1));
-int pthread_condattr_setclock(pthread_condattr_t*, clockid_t) __nonnull((1));
+int pthread_condattr_setclock(pthread_condattr_t*, clockid_t) __nonnull((1)) __INTRODUCED_IN(21);
 int pthread_condattr_setpshared(pthread_condattr_t*, int) __nonnull((1));
 
 int pthread_cond_broadcast(pthread_cond_t*) __nonnull((1));
@@ -180,7 +181,7 @@
 
 void* pthread_getspecific(pthread_key_t);
 
-pid_t pthread_gettid_np(pthread_t);
+pid_t pthread_gettid_np(pthread_t) __INTRODUCED_IN(21);
 
 int pthread_join(pthread_t, void**);
 
@@ -201,7 +202,8 @@
 #else
 int pthread_mutex_lock(pthread_mutex_t*) __nonnull((1));
 #endif
-int pthread_mutex_timedlock(pthread_mutex_t*, const struct timespec*) __nonnull((1, 2));
+int pthread_mutex_timedlock(pthread_mutex_t*, const struct timespec*) __nonnull((1, 2))
+  __INTRODUCED_IN(21);
 int pthread_mutex_trylock(pthread_mutex_t*) __nonnull((1));
 #if !defined(__LP4__)
 int pthread_mutex_unlock(pthread_mutex_t*) /* __nonnull((1)) */;
@@ -215,8 +217,9 @@
 int pthread_rwlockattr_destroy(pthread_rwlockattr_t*) __nonnull((1));
 int pthread_rwlockattr_getpshared(const pthread_rwlockattr_t*, int*) __nonnull((1, 2));
 int pthread_rwlockattr_setpshared(pthread_rwlockattr_t*, int) __nonnull((1));
-int pthread_rwlockattr_getkind_np(const pthread_rwlockattr_t*, int*) __nonnull((1, 2));
-int pthread_rwlockattr_setkind_np(pthread_rwlockattr_t*, int) __nonnull((1));
+int pthread_rwlockattr_getkind_np(const pthread_rwlockattr_t*, int*) __nonnull((1, 2))
+  __INTRODUCED_IN(23);
+int pthread_rwlockattr_setkind_np(pthread_rwlockattr_t*, int) __nonnull((1)) __INTRODUCED_IN(23);
 
 int pthread_rwlock_destroy(pthread_rwlock_t*) __nonnull((1));
 int pthread_rwlock_init(pthread_rwlock_t*, const pthread_rwlockattr_t*) __nonnull((1));
@@ -228,25 +231,28 @@
 int pthread_rwlock_unlock(pthread_rwlock_t *) __nonnull((1));
 int pthread_rwlock_wrlock(pthread_rwlock_t*) __nonnull((1));
 
-int pthread_barrierattr_init(pthread_barrierattr_t* attr) __nonnull((1));
-int pthread_barrierattr_destroy(pthread_barrierattr_t* attr) __nonnull((1));
-int pthread_barrierattr_getpshared(pthread_barrierattr_t* attr, int* pshared) __nonnull((1, 2));
-int pthread_barrierattr_setpshared(pthread_barrierattr_t* attr, int pshared) __nonnull((1));
+int pthread_barrierattr_init(pthread_barrierattr_t* attr) __nonnull((1)) __INTRODUCED_IN(24);
+int pthread_barrierattr_destroy(pthread_barrierattr_t* attr) __nonnull((1)) __INTRODUCED_IN(24);
+int pthread_barrierattr_getpshared(pthread_barrierattr_t* attr, int* pshared) __nonnull((1, 2))
+  __INTRODUCED_IN(24);
+int pthread_barrierattr_setpshared(pthread_barrierattr_t* attr, int pshared) __nonnull((1))
+  __INTRODUCED_IN(24);
 
-int pthread_barrier_init(pthread_barrier_t*, const pthread_barrierattr_t*, unsigned) __nonnull((1));
-int pthread_barrier_destroy(pthread_barrier_t*) __nonnull((1));
-int pthread_barrier_wait(pthread_barrier_t*) __nonnull((1));
+int pthread_barrier_init(pthread_barrier_t*, const pthread_barrierattr_t*, unsigned) __nonnull((1))
+  __INTRODUCED_IN(24);
+int pthread_barrier_destroy(pthread_barrier_t*) __nonnull((1)) __INTRODUCED_IN(24);
+int pthread_barrier_wait(pthread_barrier_t*) __nonnull((1)) __INTRODUCED_IN(24);
 
-int pthread_spin_destroy(pthread_spinlock_t*) __nonnull((1));
-int pthread_spin_init(pthread_spinlock_t*, int) __nonnull((1));
-int pthread_spin_lock(pthread_spinlock_t*) __nonnull((1));
-int pthread_spin_trylock(pthread_spinlock_t*) __nonnull((1));
-int pthread_spin_unlock(pthread_spinlock_t*) __nonnull((1));
+int pthread_spin_destroy(pthread_spinlock_t*) __nonnull((1)) __INTRODUCED_IN(24);
+int pthread_spin_init(pthread_spinlock_t*, int) __nonnull((1)) __INTRODUCED_IN(24);
+int pthread_spin_lock(pthread_spinlock_t*) __nonnull((1)) __INTRODUCED_IN(24);
+int pthread_spin_trylock(pthread_spinlock_t*) __nonnull((1)) __INTRODUCED_IN(24);
+int pthread_spin_unlock(pthread_spinlock_t*) __nonnull((1)) __INTRODUCED_IN(24);
 
 pthread_t pthread_self(void) __pure2;
 
 #if defined(__USE_GNU)
-int pthread_getname_np(pthread_t, char*, size_t) __nonnull((2));
+int pthread_getname_np(pthread_t, char*, size_t) __nonnull((2)) __INTRODUCED_IN(25);
 #endif
 /* TODO: this should be __USE_GNU too. */
 int pthread_setname_np(pthread_t, const char*) __nonnull((2));