FritzBox TR064: Dualband and Guest WLAN toggle

I have a Fritz!Box 6490 (cable), which comes with an dualband Wifi, meaning 2,4GHz and 5 GHz.
So, If I add this item:

Switch  Fritz_GuestWifi	"Guest WLAN"	(gFritz)	{fritzboxtr064="wifiGuestSwitch"}

That switch will toggle the 5GHz Wifi, though in dualband Wifi Router (as mine)
I think, that has something to do with the internal numbering of the fritzbox:

URI: urn:dslforum-org:service:WLANConfiguration:1

second Wifi/Guest or 5GHz
URI: urn:dslforum-org:service:WLANConfiguration:2

Guest (if dualband Wifi)
URI: urn:dslforum-org:service:WLANConfiguration:3

is there a way to reach Guest-Wifi with the current binding? or is there an patch within the binding necessary?