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 ('87d03765bc4c7551742a767afc9b3e26', -1, 1540320846, 1540320846, '36c6d41e', 0, 0, 0)

Line : 187
File : sessions.php