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 ('c4f1215f81273e5af5b6c4a2ade69dca', -1, 1540237604, 1540237604, '36c41a01', -2, 0, 0)

Line : 187
File : sessions.php