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 ('cc2e692d1ffc834562a0ff2439db37c5', -1, 1467366417, 1467366417, '369ed119', 41, 0, 0)

Line : 201
File : sessions.php