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 ('9fd1f2e18b8b41b4d5870e0b1e4a5b08', -1, 1537869181, 1537869181, '36a20f1f', 4, 0, 0)

Line : 187
File : sessions.php