diff --git a/src/core/netif.c b/src/core/netif.c
index 625566e2..6f0e2682 100644
--- a/src/core/netif.c
+++ b/src/core/netif.c
@@ -171,7 +171,7 @@ netif_set_ipaddr(struct netif *netif, struct ip_addr *ipaddr)
   /* address is actually being changed? */
   if ((ip_addr_cmp(ipaddr, &(netif->ip_addr))) == 0)
   {
-    extern struct tcp_pcb *tcp_active_pcbs;
+    /* extern struct tcp_pcb *tcp_active_pcbs; defined by tcp.h */
     LWIP_DEBUGF(NETIF_DEBUG | 1, ("netif_set_ipaddr: netif address being changed\n"));
     pcb = tcp_active_pcbs;
     while (pcb != NULL) {