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) VALUES ('6d0405918b2fc9b46a777d65dabd8369', -1, 1490611151, 1490611151, 'ac444111', 1, 0)

Line : 158
File : sessions.php