diff --git a/src/include/ipv4/lwip/ip.h b/src/include/ipv4/lwip/ip.h
index c631f324..c8b9c222 100644
--- a/src/include/ipv4/lwip/ip.h
+++ b/src/include/ipv4/lwip/ip.h
@@ -43,7 +43,6 @@
 struct netif;
 
 void ip_init(void);
-u8_t ip_lookup(void *header, struct netif *inp);
 struct netif *ip_route(struct ip_addr *dest);
 err_t ip_input(struct pbuf *p, struct netif *inp);
 err_t ip_output(struct pbuf *p, struct ip_addr *src, struct ip_addr *dest,