KVM: iphone passthrough to windows guest

I use KVM on a ubuntu 15.04 guest and a windows 7 and windows 10 guests. I connect my iPhone to my PC and want to redirect it (using virt-manager) to the guest. I always get the error.

spice-client-error-quark: Could not redirect Apple Inc. iPhone [05ac:12a0] at 1-8: Device is in use by another application (0)

the phone is not mounted in the host system. So what else can I do?

I use virtmanager, SPICE guest tools 0.100 (that's the most current version) and my ubuntu-packages (kvm...) are up-to-date.

I found the solution. libimobiledevice "captures" as soon as you try to connect it to the guest system. libimobiledevice can't be uninstalled as it is a dependency of gnome, but the package libimobiledevice-utils can be removed. This disables any interaction (even mounting) of the ubuntu host with iPhones but enables the redirection to the windows guest