diff --git a/components/net/lwip_nat/ipv4_nat.c b/components/net/lwip_nat/ipv4_nat.c
index 13c1877f2c88355b9cc8e13841d6322a2309ac3b..6f218fc1e1de8cf359a9abc8df88382dae4aa913 100644
--- a/components/net/lwip_nat/ipv4_nat.c
+++ b/components/net/lwip_nat/ipv4_nat.c
@@ -229,7 +229,7 @@ nat_timer(void *arg)
   LWIP_DEBUGF(TIMERS_DEBUG, ("tcpip: nat_timer()\n"));
 
   ip_nat_tmr();
-  sys_timeout(LWIP_NAT_TMR_INTERVAL_SEC, nat_timer, NULL);
+  sys_timeout(LWIP_NAT_TMR_INTERVAL_SEC * 1000, nat_timer, NULL);
 }
 
 /** Initialize this module */
@@ -255,7 +255,7 @@ ip_nat_init(void)
   rt_enter_critical();
 
   /* add a lwip timer for NAT */
-  sys_timeout(LWIP_NAT_TMR_INTERVAL_SEC, nat_timer, NULL);
+  sys_timeout(LWIP_NAT_TMR_INTERVAL_SEC * 1000, nat_timer, NULL);
 
   /* un-protect */
   rt_exit_critical();
diff --git a/components/net/lwip_nat/ipv4_nat.h b/components/net/lwip_nat/ipv4_nat.h
index e369c781dac1e440d466d8f20e355ee56f8739dd..b30ed984281fdeafcd272e1eb484116748b757e1 100644
--- a/components/net/lwip_nat/ipv4_nat.h
+++ b/components/net/lwip_nat/ipv4_nat.h
@@ -67,7 +67,7 @@
 #include "lwip/opt.h"
 
 /** Timer interval at which to call ip_nat_tmr() */
-#define LWIP_NAT_TMR_INTERVAL_SEC        (30*1000)
+#define LWIP_NAT_TMR_INTERVAL_SEC        (30)
 
 #ifdef __cplusplus
 extern "C" {