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 ('2aa79145e0734d24a646ea32b7592f43', -1, 1540220572, 1540220572, '3691534f', 7, 0, 0)

Line : 187
File : sessions.php