Can't login via Shibboleth while $CFG->authpreventaccountcreation is on

While testing MDL-26257 Eloy found he could not log via Shibboleth because of the following two errors (very likely related):

Coding error detected, it must be fixed by a programmer: moodle_database::update_record_raw() id field must be specified.
Stack trace:
line 961 of /lib/dml/mysqli_native_moodle_database.php: coding_exception thrown
line 1017 of /lib/dml/mysqli_native_moodle_database.php: call to mysqli_native_moodle_database->update_record_raw()
line 3073 of /lib/moodlelib.php: call to mysqli_native_moodle_database->update_record()
line 47 of /auth/shibboleth/index.php: call to update_user_login_times()

Coding error detected, it must be fixed by a programmer: Invalid $user parameter in check_user_preferences_loaded() call, missing id field

Cheers
Sam