amd64 and COMPAT_AOUT

[Daniel O'Callaghan]

I'm migrating a lot of services to a new server running 9.1 amd64.
I have a VMWare FreeBSD 3.3 server I want to decommission, which is 
running a client's website with a shopping cart system in an a.out 
binary (source code lost long ago).

I have just tried to build a new kernel on the 9.1/amd64 machine with 
COMPAT_AOUT added to /usr/src/sys/amd64/conf/NEWKERNEL but ...

root at corella:/usr/src/sys/amd64/conf # config NEWKERNEL
NEWKERNEL: unknown option "COMPAT_AOUT"

COMPAT_AOUT is recognised in i386/conf

The funny thing is that in amd64/conf/NOTES is
device          gzip            #Exec gzipped a.out's.  REQUIRES 
COMPAT_AOUT!

Is it possible to get 9.1/amd64 to run i386 a.out binaries?
What might I be missing?

Thanks,

Danny