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 ('91d2d766689c58886b6657c14e80d5ef', -1, 1539864240, 1539864240, '3650bc57', 5, 0, 0)

Line : 187
File : sessions.php