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 ('a27123cac49f8eceb2d80bb25288c0b4', -1, 1513298811, 1513298811, '36eaf776', 7, 0, 0)

Line : 189
File : sessions.php