diff --git a/libc/private/bionic_pthread.h b/libc/private/bionic_pthread.h
index 07bcbd4..28d6ad8 100644
--- a/libc/private/bionic_pthread.h
+++ b/libc/private/bionic_pthread.h
@@ -35,6 +35,7 @@
 
 /* Internal, not an NDK API */
 extern pid_t __pthread_gettid(pthread_t thid);
+extern int __pthread_settid(pthread_t thid, pid_t tid);
 
 __END_DECLS