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 ('5ea6cc9c08db408aecbf1e1bd2c986c5', -1, 1540234321, 1540234321, '36c41a01', 4, 0, 0)

Line : 187
File : sessions.php