diff --git a/libc/include/pthread.h b/libc/include/pthread.h
index 29caafc..86a1005 100644
--- a/libc/include/pthread.h
+++ b/libc/include/pthread.h
@@ -188,6 +188,8 @@
 
 void* pthread_getspecific(pthread_key_t);
 
+pid_t pthread_gettid_np(pthread_t);
+
 int pthread_join(pthread_t, void**);
 
 int pthread_key_create(pthread_key_t*, void (*)(void*)) __nonnull((1));