diff --git a/src/inet/UDPEndPointImplSockets.cpp b/src/inet/UDPEndPointImplSockets.cpp
index ffae9f1f533d34..23428fa49c4a63 100644
--- a/src/inet/UDPEndPointImplSockets.cpp
+++ b/src/inet/UDPEndPointImplSockets.cpp
@@ -21,6 +21,9 @@
  * This file implements Inet::UDPEndPoint using sockets.
  */
 
+// Required to properly support underlying RFC3542-related fields to IPV6_PKTINFO
+// on Darwin.
+#define __APPLE_USE_RFC_3542
 #include <inet/UDPEndPointImplSockets.h>
 
 #include <lib/support/CodeUtils.h>