Problems with include in acl file

[Robert Moskowitz]

I am trying to build up an environment where the user can maintain 
custom files and leave the basic files alone.

So I have a named.acl that works, I add an include line:

acl "hdanets" {
        192.168.1.0/24; // hda network
        include "custom.acl";
};


and get the error:

Starting named:
Error in named configuration:
named.acl:3: missing ';' before '"'
                                                           [FAILED]


The file custom.acl exists and it contains:

        192.168.2.0/24;

Perhaps includes are not allowed in .acl files?