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 ('399e8f8a71c0d32f79c75329f0fc2f52', -1, 1540101553, 1540101553, '36a14d1e', 16, 0, 0)

Line : 187
File : sessions.php