diff --git a/src/thread.c b/src/thread.c
index 32471bad3f..544a295eaa 100644
--- a/src/thread.c
+++ b/src/thread.c
@@ -74,7 +74,8 @@ static rt_err_t _rt_thread_init(struct rt_thread* thread,
 	thread->error = RT_EOK;
 	thread->stat  = RT_THREAD_INIT;
 
-	/* init user data */
+	/* initialize cleanup function and user data */
+	thread->cleanup = 0;
 	thread->user_data = 0;
 
 	/* init thread timer */