syntax error while using scrub with OpenBSD 4.6

Hello all,

i am fairly new to OpenBSD. I use it for a home router and firewall.
Following the recommendations, i want to use the scrub keyword.

But regardles how i write it into the pf.conf and check it with pfctl
i get a syntax error message.

I tried several syntax:

scrub all
scrub in all

After using google and other ressources for hours i found a changeset
which describes