[libvirt] XML network model type stripped on define.

Greetings! I am currently testing Centos5.3, KVM-84, libvirt from the Centos default packages and a Vista 32 guest. I am unfortunately experiencing difficulties with the default realtek8139 network driver, the solution for which I've read would be to change the emulated network device type to e1000. When editing the xml file for my guest, I change: <interface type='bridge'> <mac address='00:16:3e:38:a8:ad'/> <source bridge='br0'/> </interface> to: <interface type='bridge'> <mac address='00:16:3e:38:a8:ad'/> <source bridge='br0'/> <model type='e1000'/> </interface> and then doing a: virsh --connect qemu:///system define /etc/libvirt/qemu/vista32.xml The correct guest is updated, but the model type information I've just added is stripped from my XML and I'm once again left with an 8139 emulated nic. According to the command: qemu-kvm -net nic,model=? /dev/null I should be able to use the e1000 driver. My sincerest apologies if this is already known, or I'm missing something terribly obvious. I am new to mailing lists (this would be my first!) Thanks in advance.