phpBB : Critical Error

Error creating new session

DEBUG MODE

SQL Error : 1062 Duplicate entry '-1' for key 'session_user_id'

INSERT INTO r2ok_sessions (session_id, session_user_id, session_start, session_time, session_ip, session_page, session_logged_in, session_admin) VALUES ('affb3dc07bfdc7c7fbcc55c7418407be', -1, 1524206096, 1524206096, '3650082c', 35, 0, 0)

Line : 187
File : sessions.php