[Users] Spice client USB - Linux

Hi all, As mentioned in the features of oVirt, I should be able to use an USB-drive on my (Spice) guest.However, the option to choose an USB device is greyed out in the Spice Console. "Big Uncle" RHEV 3.1 tells in https://access.redhat.com/knowledge/docs/en-US/Red_Hat_Enterprise_Virtual... to use "Native USB" Am I missing something? Or: I tried using a serverprofile. Is USB redirection only available using a desktop profile? Anyway: how can I enable USB on my Spice Client. (Fedora 18) Kind regards, Winfried