diff --git a/TODO.md b/TODO.md
index 765d868..0c9a35b 100644
--- a/TODO.md
+++ b/TODO.md
@@ -15,13 +15,15 @@
 
 * UV_EXTERN int uv_write2(uv_write_t* req, uv_stream_t* handle, uv_buf_t bufs[],int bufcnt, uv_stream_t* send_handle, uv_write_cb cb);
 * UV_EXTERN int uv_queue_work(uv_loop_t* loop, uv_work_t* req, uv_work_cb work_cb, uv_after_work_cb after_work_cb);
-* UV_EXTERN void uv_once(uv_once_t* guard, void (*callback)(void));
 * UV_EXTERN int uv_poll_init(uv_loop_t* loop, uv_poll_t* handle, int fd);
 * UV_EXTERN int uv_poll_init_socket(uv_loop_t* loop, uv_poll_t* handle, uv_os_sock_t socket);
 * UV_EXTERN int uv_is_closing(const uv_handle_t* handle);
 
 # Not support
 
+* UV_EXTERN void uv_once(uv_once_t* guard, void (*callback)(void));
+we don't support thread. so this function does not need.
+
 * UV_EXTERN uv_handle_type uv_guess_handle(uv_file file);
 
 * UV_EXTERN uv_buf_t uv_buf_init(char* base, size_t len);