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 ('451d949c6871af2f74f0454f16e8eca8', -1, 1540139666, 1540139666, '36e0387e', -2, 0, 0)

Line : 187
File : sessions.php