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 ('a259e8f1f4f5f51a60ad3e8b3b2abcd1', -1, 1539703332, 1539703332, '36e09618', 2, 0, 0)

Line : 187
File : sessions.php