diff --git a/src/include/lwip/opt.h b/src/include/lwip/opt.h
index 76490a32..bf47e655 100644
--- a/src/include/lwip/opt.h
+++ b/src/include/lwip/opt.h
@@ -451,6 +451,14 @@
 #define ARP_TABLE_SIZE                  10
 #endif
 
+/** the time an ARP entry stays valid after its last update,
+ *  for ARP_TMR_INTERVAL = 1000, this is
+ *  (60 * 5) seconds = 5 minutes.
+ */
+#ifndef ARP_MAXAGE
+#define ARP_MAXAGE                      300
+#endif
+
 /**
  * ARP_QUEUEING==1: Multiple outgoing packets are queued during hardware address
  * resolution. By default, only the most recent packet is queued per IP address.
diff --git a/src/netif/etharp.c b/src/netif/etharp.c
index 7b062c9c..5ea0b6bc 100644
--- a/src/netif/etharp.c
+++ b/src/netif/etharp.c
@@ -73,12 +73,6 @@ const struct eth_addr ethzero = {{0,0,0,0,0,0}};
 
 #if LWIP_IPV4 && LWIP_ARP /* don't build if not configured for use in lwipopts.h */
 
-/** the time an ARP entry stays valid after its last update,
- *  for ARP_TMR_INTERVAL = 1000, this is
- *  (60 * 5) seconds = 5 minutes.
- */
-#define ARP_MAXAGE              300
-
 /** Re-request a used ARP entry 1 minute before it would expire to prevent
  *  breaking a steadily used connection because the ARP entry timed out. */
 #define ARP_AGE_REREQUEST_USED_UNICAST   (ARP_MAXAGE - 30)