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 ('e8f4887a314d5d9ffe862a6374a9d37c', -1, 1540256009, 1540256009, '36c41a01', -9, 0, 0)

Line : 187
File : sessions.php