diff --git a/src/core/netif.c b/src/core/netif.c
index 5ec5a283..b599497c 100644
--- a/src/core/netif.c
+++ b/src/core/netif.c
@@ -68,7 +68,7 @@ netif_add(struct netif *netif, struct ip_addr *ipaddr, struct ip_addr *netmask,
   err_t (* init)(struct netif *netif),
   err_t (* input)(struct pbuf *p, struct netif *netif))
 {
-  static s16_t netifnum = 0;
+  static u8_t netifnum = 0;
 
   /* reset new interface configuration state */
   netif->ip_addr.addr = 0;