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 ('7a244e5e534a0d3b770eb1354b560478', -1, 1464083721, 1464083721, '36c6648d', 10000, 0, 0)

Line : 190
File : sessions.php