Database Error!

Error: Field 'last_seen' doesn't have a default value
Query: INSERT INTO users (uid, password, ip_address, first_seen) VALUES ("5c6d65ec5e50e1.44639255", "mRChFnKgZfd2hmss7vGiHD1tssVb0C3l", "18.206.175.155", UNIX_TIMESTAMP())
File: /includes/database.class.php
Line: 98
Backtrace: