Database Error!

Error: Field 'last_seen' doesn't have a default value
Query: INSERT INTO users (uid, password, ip_address, first_seen) VALUES ("5cea32e3b9d234.45628486", "o41PJqYBJKlRFjUh50i7s0T0Rsrno1ZM", "54.227.76.35", UNIX_TIMESTAMP())
File: /includes/database.class.php
Line: 98
Backtrace: