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 ('8a981f6cfa3dc427fe7af5eb64cccb7a', -1, 1539931435, 1539931435, '36a6cfdf', -4, 0, 0)

Line : 187
File : sessions.php