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 ('ed4dd3f56ee47d0bb1f5ab60309a9117', -1, 1540103002, 1540103002, '36a14d1e', 16, 0, 0)

Line : 187
File : sessions.php