Database Error!

Error: Field 'last_seen' doesn't have a default value
Query: INSERT INTO users (uid, password, ip_address, first_seen) VALUES ("5c9690ff682d98.47908326", "3DHne8s19yu7StgM7iJLKUeWwIL7vO8M", "18.206.168.65", UNIX_TIMESTAMP())
File: /includes/database.class.php
Line: 98
Backtrace: