diff --git a/include/rtdef.h b/include/rtdef.h
index 9b12093dc7..743b91d959 100644
--- a/include/rtdef.h
+++ b/include/rtdef.h
@@ -656,6 +656,7 @@ struct rt_semaphore
     struct rt_ipc_object parent;                        /**< inherit from ipc_object */
 
     rt_uint16_t          value;                         /**< value of semaphore. */
+    rt_uint16_t          reserved;                      /**< reserved field */
 };
 typedef struct rt_semaphore *rt_sem_t;
 #endif
diff --git a/src/ipc.c b/src/ipc.c
index 7f603cfc4d..74faf6ac7e 100644
--- a/src/ipc.c
+++ b/src/ipc.c
@@ -201,6 +201,7 @@ rt_err_t rt_sem_init(rt_sem_t    sem,
                      rt_uint8_t  flag)
 {
     RT_ASSERT(sem != RT_NULL);
+    RT_ASSERT(value < 0x10000U);
 
     /* init object */
     rt_object_init(&(sem->parent.parent), RT_Object_Class_Semaphore, name);
@@ -209,7 +210,7 @@ rt_err_t rt_sem_init(rt_sem_t    sem,
     rt_ipc_object_init(&(sem->parent));
 
     /* set init value */
-    sem->value = value;
+    sem->value = (rt_uint16_t)value;
 
     /* set parent */
     sem->parent.parent.flag = flag;
@@ -261,6 +262,7 @@ rt_sem_t rt_sem_create(const char *name, rt_uint32_t value, rt_uint8_t flag)
     rt_sem_t sem;
 
     RT_DEBUG_NOT_IN_INTERRUPT;
+    RT_ASSERT(value < 0x10000U);
 
     /* allocate object */
     sem = (rt_sem_t)rt_object_allocate(RT_Object_Class_Semaphore, name);