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 ('fc0ec1d68961e8f7e228df26a7d74a65', -1, 1555612350, 1555612350, '3437bae1', 6, 0, 0)

Line : 187
File : sessions.php