diff --git a/source/portable/NetworkInterface/loopback/loopbackNetworkInterface.c b/source/portable/NetworkInterface/loopback/loopbackNetworkInterface.c
index ffe058be5c..cf486fe644 100644
--- a/source/portable/NetworkInterface/loopback/loopbackNetworkInterface.c
+++ b/source/portable/NetworkInterface/loopback/loopbackNetworkInterface.c
@@ -35,6 +35,7 @@
 #include "semphr.h"
 
 /* FreeRTOS+TCP includes. */
+#include "FreeRTOS_ARP.h"
 #include "FreeRTOS_IP.h"
 #include "FreeRTOS_Sockets.h"
 #include "FreeRTOS_IP_Private.h"