Configure can't find com_err on OpenBSD for --with-krb5

I am trying to build PostgreSQL 8.2.3 on OpenBSD 4.0. When I give the
command

./configure -v --with-openssl --with-krb5
--with-includes=/usr/include/kerberosV

I get:

checking for library containing com_err... no
configure: error: could not find function 'com_err' required for Kerberos 5

This is puzzling, because com_err.o is clearly listed in libkrb5.a. Any
thoughts on how to get this to build would be appreciated.

-Thanks, Jim