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 ('e37575cec7fd4d66d739d2425399b615', -1, 1422346842, 1422346842, '36edf7ac', -1, 0, 0)

Line : 189
File : sessions.php