diff --git a/src/nwfilter/nwfilter_learnipaddr.c b/src/nwfilter/nwfilter_learnipaddr.c
index 7c94fc24ce..7fc55a67e7 100644
--- a/src/nwfilter/nwfilter_learnipaddr.c
+++ b/src/nwfilter/nwfilter_learnipaddr.c
@@ -38,6 +38,11 @@
 #include <net/if_arp.h>
 #include <intprops.h>
 
+// Add Linux define missing from OSX
+#ifndef ETH_ALEN
+# define ETH_ALEN       6               /* Octets in one ethernet addr   */
+#endif
+
 #include "internal.h"
 
 #include "buf.h"