phpBB : Critical Error

Error creating new session

DEBUG MODE

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

INSERT INTO forum_sessions (session_id, session_user_id, session_start, session_time, session_ip, session_page, session_logged_in, session_admin) VALUES ('3504dcb8a6515ab89fc8208df523ec34', -1, 1540343240, 1540343240, '36a16418', 9, 0, 0)

Line : 187
File : sessions.php