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 ('e1b0d8d8ac21f280e2756c0d52180b82', -1, 1422681939, 1422681939, '36c6669c', -1, 0)

Line : 158
File : sessions.php