phpBB : Critical Error

Error creating new session

DEBUG MODE

SQL Error : 1062 Duplicate entry '-1' for key 'session_user_id'

INSERT INTO forum_sessions (session_id, session_user_id, session_start, session_time, session_ip, session_page, session_logged_in, session_admin) VALUES ('d011a3db731a0fc996bca66b7a0395de', -1, 1540087971, 1540087971, '3650bc57', 3, 0, 0)

Line : 187
File : sessions.php