pam_access.so not recognizing host name in access.conf

Hi,
The following specification in access.conf does not work as expected:
-:username:ALL EXCEPT localhost
The manual page access.conf.5 claims that the third field may contain
host names, but the code only checks for numerical IP addresses by
calling inet_pton().
Is this desired behavior or am I missing something.
I'm willing to write a patch.
Josef