diff --git a/libc/bionic/pthread_mutex.cpp b/libc/bionic/pthread_mutex.cpp
index 4fec753..851fc3d 100644
--- a/libc/bionic/pthread_mutex.cpp
+++ b/libc/bionic/pthread_mutex.cpp
@@ -501,6 +501,12 @@
 }
 
 int pthread_mutex_lock(pthread_mutex_t* mutex_interface) {
+#if !defined(__LP64__)
+    if (mutex_interface == NULL) {
+        return EINVAL;
+    }
+#endif
+
     pthread_mutex_internal_t* mutex = __get_internal_mutex(mutex_interface);
 
     uint16_t old_state = atomic_load_explicit(&mutex->state, memory_order_relaxed);
@@ -516,6 +522,12 @@
 }
 
 int pthread_mutex_unlock(pthread_mutex_t* mutex_interface) {
+#if !defined(__LP64__)
+    if (mutex_interface == NULL) {
+        return EINVAL;
+    }
+#endif
+
     pthread_mutex_internal_t* mutex = __get_internal_mutex(mutex_interface);
 
     uint16_t old_state = atomic_load_explicit(&mutex->state, memory_order_relaxed);
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));