phpBB : Critical Error

Error creating new session

DEBUG MODE

SQL Error : 1062 Duplicate entry '-1' for key 'phpbb_sessions.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 ('b9172fac3fa5b8106da3b127d7e1bcb4', -1, 1768185888, 1768185888, 'd849d897', 10, 0, 0)

Line : 187
File : sessions.php