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 ('23bf516ad1ad7af35b1acd358e122908', -1, 1540111975, 1540111975, '36e0387e', -4, 0, 0)

Line : 187
File : sessions.php