--- src/openvpn/lladdr.c
+++ src/openvpn/lladdr.c
@@ -26,6 +26,10 @@
         return -1;
     }
 
+#ifndef ETH_ALEN
+#define ETH_ALEN        6               /* Octets in one ethernet addr   */
+#endif
+
 #if defined(TARGET_LINUX)
     uint8_t addr[OPENVPN_ETH_ALEN];
 
--- src/openvpn/networking_sitnl.c
+++ src/openvpn/networking_sitnl.c
@@ -56,6 +56,10 @@
 #define NLMSG_TAIL(nmsg) \
     ((struct rtattr *)(((uint8_t *)(nmsg)) + NLMSG_ALIGN((nmsg)->nlmsg_len)))
 
+#ifndef ETH_ALEN
+#define ETH_ALEN        6               /* Octets in one ethernet addr   */
+#endif
+
 /**
  * Generic address data structure used to pass addresses and prefixes as
  * argument to AF family agnostic functions