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 ('989969b7ea59cf3784d820a4bd32a2cd', -1, 1406762163, 1406762163, '17143214', 83, 0, 0)

Line : 180
File : sessions.php