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 ('6e9c623997bbce337e0f9d3d20982868', -1, 1529753796, 1529753796, '36901087', 36, 0, 0)

Line : 187
File : sessions.php