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 ('4ef2eae1c53ebbb03aeb8d319e7f5a2f', -1, 1539634449, 1539634449, '36a6829d', 3, 0, 0)

Line : 187
File : sessions.php