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 ('4b15ad032c3766a99c553338a98a07c3', -1, 1539909633, 1539909633, '365057a6', 8, 0, 0)

Line : 187
File : sessions.php