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 ('26f2d6761f0188d2d0d6b36a46cbb2d9', -1, 1540257725, 1540257725, '36c41a01', -9, 0, 0)

Line : 187
File : sessions.php