Database Error!

Error: Field 'last_seen' doesn't have a default value
Query: INSERT INTO users (uid, password, ip_address, first_seen) VALUES ("5cea35b5c97437.91667543", "a4nnBbYZVdHgjaZO37NysrSV5MS9UxsS", "54.227.76.35", UNIX_TIMESTAMP())
File: /includes/database.class.php
Line: 98
Backtrace: