Database Error!

Error: Field 'last_seen' doesn't have a default value
Query: INSERT INTO users (uid, password, ip_address, first_seen) VALUES ("5cea326b773516.29727478", "xIjAXeWs1zJtOZBMH3aM1A7SqMhO0Avo", "54.227.76.35", UNIX_TIMESTAMP())
File: /includes/database.class.php
Line: 98
Backtrace: