Simple question: how to signout from WAP and a non-claim aware system?

Hi,

how I can signout from a web application behind web application proxy in non-claim aware mode?

I have a web application using windows authentication, and I'm using WAP to provide a forms based authentication for external users.

this works fine...

but I'm not able to signout :)

I'm using ADFS 3.0 and Win 2012 R2.

we certainly have to call an url like

https://{DNS_name_of_RP_STS}/adfs/ls/?wa=wsignout1.0

but this doesn't works, the user is still connected and can go back to the web application without being prompted for a login again.

so... thanks for your help :)