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 ('dbe95bd3c3baacb99016ab789b1e7412', -1, 1464083653, 1464083653, '36c6648d', 10018, 0, 0)

Line : 190
File : sessions.php