diff --git a/src/include/lwip/api.h b/src/include/lwip/api.h
index 2537f1cd..2e6561e0 100644
--- a/src/include/lwip/api.h
+++ b/src/include/lwip/api.h
@@ -154,7 +154,7 @@ struct netconn {
   /** mbox where new connections are stored until processed
       by the application thread */
   sys_mbox_t acceptmbox;
-#endif LWIP_TCP
+#endif /* LWIP_TCP */
   /** only used for socket layer */
 #if LWIP_SOCKET
   int socket;