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 ('f5ac84449cd028e1b3aac5c50e6d5f8c', -1, 1540341434, 1540341434, '36a16418', -2, 0, 0)

Line : 187
File : sessions.php