diff --git a/target/linux/mvebu/base-files/lib/preinit/06_set_iface_mac b/target/linux/mvebu/base-files/lib/preinit/06_set_iface_mac
index 30f1370b8f..2b64eda822 100644
--- a/target/linux/mvebu/base-files/lib/preinit/06_set_iface_mac
+++ b/target/linux/mvebu/base-files/lib/preinit/06_set_iface_mac
@@ -11,8 +11,9 @@ preinit_set_mac_address() {
 	case $(mvebu_board_name) in
 	armada-xp-mamba)
 		mac=$(mtd_get_mac_ascii devinfo hw_mac_addr)
+		mac_wan=$(macaddr_setbit_la "$mac")
 		ifconfig eth0 hw ether $mac 2>/dev/null
-		ifconfig eth1 hw ether $mac 2>/dev/null
+		ifconfig eth1 hw ether $mac_wan 2>/dev/null
 		;;
 	esac
 }