Reference: bnc#813082

Index: virt-manager-0.10.0/virtinst/VirtualDisk.py
===================================================================
--- virt-manager-0.10.0.orig/virtinst/VirtualDisk.py
+++ virt-manager-0.10.0/virtinst/VirtualDisk.py
@@ -1177,6 +1177,11 @@ class VirtualDisk(VirtualDevice):
             if drvname == self.DRIVER_QEMU:
                 drvtype = _qemu_sanitize_drvtype(self.type, self.format,
                                                  manual_format=True)
+            else:
+                drvtype = self.format
+                drvtypes = ['qcow2', 'vmdk']
+                if drvtype in drvtypes and drvname is None:
+                    drvname = 'tap'
 
         elif self.vol_object:
             fmt = util.get_xml_path(self.vol_object.XMLDesc(0),