diff --git a/sys/include/net/arp.h b/sys/include/net/arp.h
index 8d164ba323..844e4fca9b 100644
--- a/sys/include/net/arp.h
+++ b/sys/include/net/arp.h
@@ -32,6 +32,7 @@ extern "C" {
  * @{
  */
 #define ARP_HWTYPE_ETHERNET (1U)        /**< Ethernet */
+#define ARP_HWTYPE_SERIAL   (20U)       /**< Serial Line */
 #define ARP_HWTYPE_EUI64    (27U)       /**< EUI-64 */
 /** @} */
 
diff --git a/sys/net/gnrc/application_layer/dhcpv6/client.c b/sys/net/gnrc/application_layer/dhcpv6/client.c
index d9d4fe80c6..960960d3dc 100644
--- a/sys/net/gnrc/application_layer/dhcpv6/client.c
+++ b/sys/net/gnrc/application_layer/dhcpv6/client.c
@@ -52,6 +52,11 @@ unsigned dhcpv6_client_get_duid_l2(unsigned iface, dhcpv6_duid_l2_t *duid)
     }
     else {
         switch (netif->device_type) {
+            case NETDEV_TYPE_SLIP:
+                duid->l2type = byteorder_htons(ARP_HWTYPE_SERIAL);
+                /* L2 address length is 0 */
+                res = 0;
+                break;
             case NETDEV_TYPE_ETHERNET:
             case NETDEV_TYPE_BLE:
             case NETDEV_TYPE_ESP_NOW: