diff --git a/src/include/lwip/api.h b/src/include/lwip/api.h
index e2d926aa..87c471a5 100644
--- a/src/include/lwip/api.h
+++ b/src/include/lwip/api.h
@@ -48,6 +48,10 @@
 extern "C" {
 #endif
 
+/* Throughout this file, IP addresses and port numbers are expected to be in
+ * the same byte order as in the corresponding pcb.
+ */
+
 #define NETCONN_NOCOPY 0x00
 #define NETCONN_COPY   0x01
 
diff --git a/src/include/lwip/api_msg.h b/src/include/lwip/api_msg.h
index 3dd39e5f..268cc656 100644
--- a/src/include/lwip/api_msg.h
+++ b/src/include/lwip/api_msg.h
@@ -47,6 +47,9 @@
 extern "C" {
 #endif
 
+/* IP addresses and port numbers are expected to be in
+ * the same byte order as in the corresponding pcb.
+ */
 struct api_msg_msg {
   struct netconn *conn;
   enum netconn_type conntype;
diff --git a/src/include/lwip/netif.h b/src/include/lwip/netif.h
index 252c8581..562e9a1a 100644
--- a/src/include/lwip/netif.h
+++ b/src/include/lwip/netif.h
@@ -48,6 +48,9 @@
 extern "C" {
 #endif
 
+/* Throughout this file, IP addresses are expected to be in
+ * the same byte order as in IP_PCB. */
+
 /** must be the maximum of all used hardware address lengths
     across all types of interfaces in use */
 #define NETIF_MAX_HWADDR_LEN 6U
@@ -175,7 +178,7 @@ struct netif *netif_find(char *name);
 void netif_set_default(struct netif *netif);
 
 void netif_set_ipaddr(struct netif *netif, struct ip_addr *ipaddr);
-void netif_set_netmask(struct netif *netif, struct ip_addr *netmast);
+void netif_set_netmask(struct netif *netif, struct ip_addr *netmask);
 void netif_set_gw(struct netif *netif, struct ip_addr *gw);
 void netif_set_up(struct netif *netif);
 void netif_set_down(struct netif *netif);