Can't log in as root when require_auditd is set in PAM configuration files (sshd and login)

Issue

When adding the following to /etc/pam.d/sshd:

session required pam_loginuid.so require_auditd

root can't login via ssh anymore, with the following messages logged in /var/log/secure:

Aug 27 16:46:17 rhel6 sshd[1654]: Accepted password for root from ::1 port 47123 ssh2
Aug 27 16:46:17 rhel6 sshd[1654]: pam_unix(sshd:session): session opened for user root by (uid=0)
Aug 27 16:46:17 rhel6 sshd[1654]: error: PAM: pam_open_session(): Cannot make/remove an entry for the specified session
Aug 27 16:46:17 rhel6 sshd[1654]: Received disconnect from ::1: 11: disconnected by user

Login via sshd works fine when require_auditd is not present in sshd's PAM configuration file.

auditd is running at the time of the tests.