DUID wan1 interface

Hi,

I've enabled IPv6 on my Fortigate 60D. 

My ISP allows me to use a "fixed" ipv6 subnet which will be assigned to my wan interface via dhcp.

In order to obtain this "fixed" ipv6 subnet via dhcp, I need to register my DUID through my ISP's portal.

I cannot find the DUID for the wan1 interface.

I already enabled an IPv6 DHCP server on my fortigate's LAN interface and I can see the DUID from my LAN-clients, but I can't find my fortigate 60d's DUID to register with my ISP.

Any clues?

Version: FortiGate-60D v5.4.0,build1011,151221 (GA)