Database Error!

Error: Field 'last_seen' doesn't have a default value
Query: INSERT INTO users (uid, password, ip_address, first_seen) VALUES ("5c681ff7e76a90.35892580", "F3vDCCbx6BO0OFgUp7ZJWnWuGeqcOOUY", "34.207.152.62", UNIX_TIMESTAMP())
File: /includes/database.class.php
Line: 98
Backtrace: