phpBB : Critical Error

Error creating new session

DEBUG MODE

SQL Error : 1062 Duplicate entry '-1' for key 'session_user_id'

INSERT INTO phpbb_sessions (session_id, session_user_id, session_start, session_time, session_ip, session_page, session_logged_in, session_admin) VALUES ('c5c1723e380766a8b9d401dc2930dcd8', -1, 1539866507, 1539866507, '36c637a7', 2, 0, 0)

Line : 187
File : sessions.php