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 ('40f5fbe12e35d7346fb88a3ff14a0c4f', -1, 1539864137, 1539864137, '3650bc57', 9, 0, 0)

Line : 187
File : sessions.php