diff --git a/include/rtdef.h b/include/rtdef.h
index e5b862b328..c5a87510f2 100644
--- a/include/rtdef.h
+++ b/include/rtdef.h
@@ -323,7 +323,7 @@ struct rt_thread
 	void*		entry;									/* entry 									*/
 	void*       parameter;								/* parameter 								*/
 	void*       stack_addr;								/* stack address 							*/
-	rt_uint32_t stack_size;								/* stack size 								*/
+	rt_uint16_t stack_size;								/* stack size 								*/
 
 	/* error code */
 	rt_err_t    error;									/* error code 								*/