4.2 and 4.3 BIND: masters_list does not work with masters option

[Jacob Yocom-Piatt]

afaict as of BIND 9.3.2 use of an acl in the masters option was 
supported, e.g.

acl int_masters {
   10.0.0.1;
};
...

       zone "somedomain.com" {
               type slave;
               masters { int_masters; };
               file "slave/internal/somedomain.com";
       };

but apparently named does not parse this and complains that it is

'unable to find masters list 'int_masters''

any clues as to what is going on here? i'm following the only explicit 
example i was able to find about this:

http://docs.hp.com/en/5992-3347/ch01s03.html

cheers,
jake