phpBB : Critical Error

Error creating new session

DEBUG MODE

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

INSERT INTO z_sessions (session_id, session_user_id, session_start, session_time, session_ip, session_page, session_logged_in, session_admin) VALUES ('558d1568dba9862c1baddc76e4f881bc', -1, 1537412376, 1537412376, '36c6670d', -1, 0, 0)

Line : 188
File : sessions.php