Filter OSPF to kernel routes

[Marcus Büttemeyer]

Hello,
I'm distributing my default route via OSPFv3 from my edge router. For
testing purposes I would like to ignore that default route on one of my
routers. Said router gets a default route via IPv6 router advertisements
but the OSPF route is preferred. So I tried:

filter default-reject {
        if ::/0 ~ net then reject;
}
[...]
protocol ospf v3 ospfv3 {
  ipv6 {
    import filter default-reject;
[...] and
protocol kernel kernel6 {
  ipv6 { export filter default-reject; };
[...]
The filter seems to be correct, "show route filter ..." works in birdc. But
I still have the OSPF default route. So it seems I misunderstand filters in
BIRD completely. Can anybody point me in the right direction?

Thanks in advance,
Marcus Büttemeyer