no support for virtual interfases in openbsd bridging?

[Rigormortis Zalman <obsd@horrifying.net>]

i have 802.1Q vlan tagging enabled on virtual interfase vlan0 and wanted
to use openbsd as a bridge inbetween 2 lans with vlan0 and xl0 and it
likes xl0 just fine but i get this when i try to add vlan0 to bridge0

bash-2.04# brconfig bridge0 add vlan0
brconfig: bridge0: vlan0: Invalid argument

it adds xl0 fine though.  looking at the kernel config i think it only
supports 2 devices but vlan0 and xl0 are only 2.  am i doing something
wrong or is there a known workarround?