Restrict VPN SSL access to windows devices only

Hi,

I just configured VPN SSL access to our remote users in our Fortigate 600D cluster, however due to company´s security policy only authorized Windows PCs are permitted to connect using this service. Anyone knows If there is anyway that I can forbid android/IOS clients to connect. I have tried to use device detection but is not working for the SSL.root interface.

Thanks in advance.

Regards