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 ('31f3ba2eaaf7b8f6dd532c13ace8603e', -1, 1540131979, 1540131979, '36e05922', 5, 0, 0)

Line : 187
File : sessions.php