diff --git a/libc/include/pthread.h b/libc/include/pthread.h
index 26d68e4..260ae5b 100644
--- a/libc/include/pthread.h
+++ b/libc/include/pthread.h
@@ -176,10 +176,18 @@
 
 int pthread_mutex_destroy(pthread_mutex_t*) __nonnull((1));
 int pthread_mutex_init(pthread_mutex_t*, const pthread_mutexattr_t*) __nonnull((1));
+#if !defined(__LP64__)
+int pthread_mutex_lock(pthread_mutex_t*) /* __nonnull((1)) */;
+#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_trylock(pthread_mutex_t*) __nonnull((1));
+#if !defined(__LP4__)
+int pthread_mutex_unlock(pthread_mutex_t*) /* __nonnull((1)) */;
+#else
 int pthread_mutex_unlock(pthread_mutex_t*) __nonnull((1));
+#endif
 
 int pthread_once(pthread_once_t*, void (*)(void)) __nonnull((1, 2));