libvirt.xml.template 'root=' kernel option conflicting with disc name with Xen

The libvirt.xml.template provided by the package python-nova in the openstack ppa has the following lines:

#if $type == 'xen'
        #set $disk_bus = 'scsi'
            <type>linux</type>
            #set $root_device_name = $getVar('root_device_name', '/dev/xvda')
            <root>${root_device_name}</root>

This lines set the "root=" option in the kernel line to /dev/xvda, but the disc is auto-detected as sda. So the libvirt.xml.template should rename "/dev/xvda" ti "/dev/sda" or the driver auto-detection should name the disc driver xvda.