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 ('31c33aecda9f73eb3e6dae28333eddd4', -1, 1539850316, 1539850316, '36a16418', -4, 0, 0)

Line : 187
File : sessions.php