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 ('a8026b812f2fc756e49e54361d5f6f01', -1, 1566081741, 1566081741, '03511c5e', -9, 0, 0)

Line : 172
File : /home/rebkell/public_html/boards/includes/sessions.php