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 ('84ff133afb1f340bca63c73759ea19eb', -1, 1555615316, 1555615316, '3437bae1', 9, 0, 0)

Line : 187
File : sessions.php