10.in-addr.arpa Forwarder Zone

[Eric R]

I have configured a simple forward zone like the following in BIND:

zone "3.10.in-addr.arpa" {
        type forward;
        forward only;
        forwarders { 1.2.3.4; } ;
};

This is the only zone I have configured.

When I query for, as an example, 1.2.3.10.inaddr.arpa (PTR), I expect BIND to query the 1.2.3.4 forwarder and return the response provided by 1.2.3.4.  With BIND version 9.6.1-P1, this works as expected. However with version 9.9.1-P3, BIND does not attempt to query the forwarder and instead immediately returns an NXDOMAIN response.

I found that adding the following zone, in addition to or instead of the original, produces the desired results:

zone "10.in-addr.arpa" {
        type forward;
        forward only;
        forwarders { 1.2.3.4; } ;
};

However, I do not wish to send all 10.in-addr.arpa queries to the forwarder; I only wish to send descendants of 3.10.in-addr.arpa there.

Is this a bug in BIND 9.9.1-P3?  I do not understand why the only zone configured would not be used, since it does appear to be the nearest (and only) ancestor of the domain I am querying.