syntax error while using scrub with OpenBSD 4.6

Hello all,

[ the formerly post was not complete because of my web-session was crashed ].

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 scrub to use

match in all scrub (random-id fragment reassemble tcp)

If i try to activate this, i got a syntax error. What have i done wrong?

Best regards