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 ('a2e930d5c4c068b9fb14f241a148a253', -1, 1529844449, 1529844449, '36916745', -4, 0, 0)

Line : 187
File : sessions.php