diff --git a/src/include/netif/lowpan6.h b/src/include/netif/lowpan6.h
index 21552938..4174644b 100644
--- a/src/include/netif/lowpan6.h
+++ b/src/include/netif/lowpan6.h
@@ -73,7 +73,9 @@ err_t lowpan6_if_init(struct netif *netif);
 /* pan_id in network byte order. */
 err_t lowpan6_set_pan_id(u16_t pan_id);
 
+#if !NO_SYS
 err_t tcpip_6lowpan_input(struct pbuf *p, struct netif *inp);
+#endif /* !NO_SYS */
 
 #ifdef __cplusplus
 }
diff --git a/src/netif/lowpan6.c b/src/netif/lowpan6.c
index b073efd4..407848c4 100644
--- a/src/netif/lowpan6.c
+++ b/src/netif/lowpan6.c
@@ -1186,6 +1186,7 @@ lowpan6_set_pan_id(u16_t pan_id)
   return ERR_OK;
 }
 
+#if !NO_SYS
 /**
  * Pass a received packet to tcpip_thread for input processing
  *
@@ -1198,5 +1199,6 @@ tcpip_6lowpan_input(struct pbuf *p, struct netif *inp)
 {
   return tcpip_inpkt(p, inp, lowpan6_input);
 }
+#endif /* !NO_SYS */
 
 #endif /* LWIP_IPV6 && LWIP_6LOWPAN */