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 ('967557773504a557d4aa194aa117be95', -1, 1540137075, 1540137075, '36a285de', -2, 0, 0)

Line : 187
File : sessions.php