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 ('fbf6b088d6160ee96f0a6f30d1ee7ded', -1, 1529804647, 1529804647, '3650c6ad', 37, 0, 0)

Line : 187
File : sessions.php