diff --git a/components/net/lwip-1.4.0/src/arch/sys_arch.c b/components/net/lwip-1.4.0/src/arch/sys_arch.c
index 4c4c120670..18ab84e46f 100644
--- a/components/net/lwip-1.4.0/src/arch/sys_arch.c
+++ b/components/net/lwip-1.4.0/src/arch/sys_arch.c
@@ -27,7 +27,7 @@ err_t sys_sem_new(sys_sem_t *sem, u8_t count)
 	char tname[RT_NAME_MAX];
 	sys_sem_t tmpsem;
 
-	RT_DEBUG_NOT_IN_INTERRUPT
+	RT_DEBUG_NOT_IN_INTERRUPT;
 
 	rt_snprintf(tname, RT_NAME_MAX, "%s%d", SYS_LWIP_SEM_NAME, counter);
 
@@ -55,7 +55,7 @@ err_t sys_sem_new(sys_sem_t *sem, u8_t count)
 
 void sys_sem_free(sys_sem_t *sem)
 {
-	RT_DEBUG_NOT_IN_INTERRUPT
+	RT_DEBUG_NOT_IN_INTERRUPT;
 
 #if SYS_DEBUG
 	{
@@ -94,7 +94,7 @@ u32_t sys_arch_sem_wait(sys_sem_t *sem, u32_t timeout)
 	s32_t t;
 	u32_t tick;
 
-	RT_DEBUG_NOT_IN_INTERRUPT
+	RT_DEBUG_NOT_IN_INTERRUPT;
 	
 	/* get the begin tick */
 	tick = rt_tick_get();
@@ -167,7 +167,7 @@ err_t sys_mutex_new(sys_mutex_t *mutex)
 	char tname[RT_NAME_MAX];
 	sys_mutex_t tmpmutex;
 
-	RT_DEBUG_NOT_IN_INTERRUPT
+	RT_DEBUG_NOT_IN_INTERRUPT;
 
 	rt_snprintf(tname, RT_NAME_MAX, "%s%d", SYS_LWIP_MUTEX_NAME, counter);
 
@@ -197,7 +197,7 @@ err_t sys_mutex_new(sys_mutex_t *mutex)
 void sys_mutex_lock(sys_mutex_t *mutex)
 {
 
-	RT_DEBUG_NOT_IN_INTERRUPT
+	RT_DEBUG_NOT_IN_INTERRUPT;
 
 #if SYS_DEBUG
 	{
@@ -236,7 +236,7 @@ void sys_mutex_unlock(sys_mutex_t *mutex)
  * @param mutex the mutex to delete */
 void sys_mutex_free(sys_mutex_t *mutex)
 {
-	RT_DEBUG_NOT_IN_INTERRUPT
+	RT_DEBUG_NOT_IN_INTERRUPT;
 
 #if SYS_DEBUG
 	{
@@ -275,7 +275,7 @@ err_t sys_mbox_new(sys_mbox_t *mbox, int size)
 	char tname[RT_NAME_MAX];
 	sys_mbox_t tmpmbox;
 
-	RT_DEBUG_NOT_IN_INTERRUPT
+	RT_DEBUG_NOT_IN_INTERRUPT;
 
 	rt_snprintf(tname, RT_NAME_MAX, "%s%d", SYS_LWIP_MBOX_NAME, counter);
 
@@ -302,7 +302,7 @@ err_t sys_mbox_new(sys_mbox_t *mbox, int size)
 
 void sys_mbox_free(sys_mbox_t *mbox)
 {
-	RT_DEBUG_NOT_IN_INTERRUPT
+	RT_DEBUG_NOT_IN_INTERRUPT;
 
 #if SYS_DEBUG
 	{
@@ -325,7 +325,7 @@ void sys_mbox_free(sys_mbox_t *mbox)
  * @param msg message to post (ATTENTION: can be NULL) */
 void sys_mbox_post(sys_mbox_t *mbox, void *msg)
 {
-	RT_DEBUG_NOT_IN_INTERRUPT
+	RT_DEBUG_NOT_IN_INTERRUPT;
 
 #if SYS_DEBUG
 	{
@@ -373,7 +373,7 @@ u32_t sys_arch_mbox_fetch(sys_mbox_t *mbox, void **msg, u32_t timeout)
 	s32_t t;
 	u32_t tick;
 
-	RT_DEBUG_NOT_IN_INTERRUPT
+	RT_DEBUG_NOT_IN_INTERRUPT;
 
 	/* get the begin tick */
 	tick = rt_tick_get();
@@ -395,8 +395,7 @@ u32_t sys_arch_mbox_fetch(sys_mbox_t *mbox, void **msg, u32_t timeout)
 		return SYS_ARCH_TIMEOUT;
 	else
 	{
-		if (ret == RT_EOK)
-			ret = 1;
+		LWIP_ASSERT("rt_mb_recv returned with error!", ret == RT_EOK);
 	}
 
 #if SYS_DEBUG
@@ -477,7 +476,7 @@ sys_thread_t sys_thread_new(const char *name, lwip_thread_fn thread, void *arg,
 {
 	rt_thread_t t;
 
-	RT_DEBUG_NOT_IN_INTERRUPT
+	RT_DEBUG_NOT_IN_INTERRUPT;
 
 	/* create thread */
 	t = rt_thread_create(name, thread, arg, stacksize, prio, 20);
diff --git a/components/net/lwip-1.4.0/src/netif/ethernetif.c b/components/net/lwip-1.4.0/src/netif/ethernetif.c
index 9ebb9f8281..1029b46512 100644
--- a/components/net/lwip-1.4.0/src/netif/ethernetif.c
+++ b/components/net/lwip-1.4.0/src/netif/ethernetif.c
@@ -94,7 +94,7 @@ static err_t ethernetif_linkoutput(struct netif *netif, struct pbuf *p)
 	struct eth_tx_msg msg;
 	struct eth_device* enetif;
 
-	RT_DEBUG_NOT_IN_INTERRUPT
+	RT_DEBUG_NOT_IN_INTERRUPT;
 
 	enetif = (struct eth_device*)netif->state;
 
@@ -119,7 +119,7 @@ static struct eth_device* eth_dev;
 static err_t ethernetif_init(struct netif *netif)
 {
 
-	RT_DEBUG_NOT_IN_INTERRUPT
+	RT_DEBUG_NOT_IN_INTERRUPT;
 
 	if( (eth_dev == RT_NULL) || (eth_dev->netif != netif) )
 		return ERR_MEM;
@@ -164,7 +164,7 @@ rt_err_t eth_device_init(struct eth_device* dev, const char* name)
 {
 	struct netif* pnetif;
 
-	RT_DEBUG_NOT_IN_INTERRUPT
+	RT_DEBUG_NOT_IN_INTERRUPT;
 
 	/* allocate memory */
 	pnetif = (struct netif*) rt_malloc (sizeof(struct netif));
diff --git a/components/net/lwip/src/arch/sys_arch.c b/components/net/lwip/src/arch/sys_arch.c
index 57ead3d755..a03150f6d9 100644
--- a/components/net/lwip/src/arch/sys_arch.c
+++ b/components/net/lwip/src/arch/sys_arch.c
@@ -156,9 +156,13 @@ u32_t sys_arch_mbox_fetch(sys_mbox_t mbox, void **msg, u32_t timeout)
 	}
 
 	ret = rt_mb_recv(mbox, (rt_uint32_t *)msg, t);
-
-	if(ret == -RT_ETIMEOUT) return SYS_ARCH_TIMEOUT;
-	else if (ret == RT_EOK) ret = 1;
+	
+	if(ret == -RT_ETIMEOUT)
+		return SYS_ARCH_TIMEOUT;
+	else
+	{
+		LWIP_ASSERT("rt_mb_recv returned with error!", ret == RT_EOK);
+	}
 
 	LWIP_DEBUGF(SYS_DEBUG, ("%s, Fetch mail: %s , 0x%x\n", LWIP_THREAD_NAME,
 		mbox->mb->parent.parent.name, *(rt_uint32_t **)msg));