Problems creating reverse ip6.arp zone with bitstrings

[Julius Schwartzenberg]

Hi,

I'm having some trouble creating a proper zone file for my reverse 
ip6.arp zone with bitstrings. My normal zone & ip6.int zone are already 
working.

For the prefix: 2001:1234:5678
On top of my zone file I have:
$ORIGIN \[x200112345678/48].ip6.arpa.

When running named-checkzone it says:
dns_master_load: /etc/bind/db.2001:1234:5678.ip6.arpa:2: ignoring 
out-of-zone data (\[x200112345678/48].ip6.arpa)

Also \[x00000000000000000001/48] and similar are called 'bad bitstring'.

I've searched, but I haven't been able to find much documentation about 
this.
What am I doing wrong?
I'm using BIND 9.2.4 (from Debian 3.1).

Thanks in advance,

Julius