phpBB : Critical Error

Error creating new session

DEBUG MODE

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

INSERT INTO phpbb_sessions (session_id, session_user_id, session_start, session_time, session_ip, session_page, session_logged_in, session_admin) VALUES ('92bd54c09b367ca8b0b286cc13353124', -1, 1529940378, 1529940378, '36e0ebb7', -8, 0, 0)

Line : 172
File : sessions.php