[ovirt-users] mixing tagged and untagged vlans on a same interface

Hi all, On a standalone libvirt/KVM, I've been used to mix tagged and untagged vlans on the same interface, the untagged vlan dedicated to the physical interface em1 and the other tagged ones to VLAN em1.X. I've just installed a new datacenter with an untagged ovirtmgmt and then realized that I've been prevented from attaching additional vlan to the same inetrface. Is there a reason for that, knowing that nothing should technically be wrong?