proxy_store skip not 200

[vps4]

i setup proxy_store works fine, but has some problem
when the backend response 404 or other result, proxy_store still save them
for example:

backend 1.jpg response 404 and html result, proxy_store will store it in
disk
how can i skip that results not 200 and verify by mime etc...

thanks

Posted at Nginx Forum: https://forum.nginx.org/read.php?2,263110,263110#msg-263110