phpBB by Przemo : 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 ('72cf46a4ddb4e467360fd5009a9eb4c5', -1, 1467038791, 1467038791, '67e3933a', 16, 0, 0)

Line : 445
File : sessions.php