Database Error!

Error: Field 'last_seen' doesn't have a default value
Query: INSERT INTO users (uid, password, ip_address, first_seen) VALUES ("5c96e6f4a9ce29.92127593", "LFNSvjZm9l6cdCLJ0YfRXquqHMeCWEbP", "107.23.176.162", UNIX_TIMESTAMP())
File: /includes/database.class.php
Line: 98
Backtrace: