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 ('37c0512c40c9cc50e7bf409b1f06f424', -1, 1540089390, 1540089390, '3650bc57', -1, 0, 0)

Line : 187
File : sessions.php