phpBB : Critical Error

Error creating new session

DEBUG MODE

SQL Error : 1062 Duplicate entry '-1' for key 'session_user_id'

INSERT INTO forum_sessions (session_id, session_user_id, session_start, session_time, session_ip, session_page, session_logged_in, session_admin) VALUES ('e519e618c36b8e78b587d133ccd55aa4', -1, 1540216988, 1540216988, '36a16418', 0, 0, 0)

Line : 187
File : sessions.php