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 ('ab824daf1b61a7e9c8bf4be452a2844f', -1, 1513298877, 1513298877, '36eaf776', 1, 0, 0)

Line : 189
File : sessions.php