proxy_pass $arg_uri Do not decode URL

[minutero]

nginx 1.12.2

I have a location rule like this to proxy external images:

        location /imagesproxy {
        resolver 8.8.8.8;
        proxy_pass $arg_uri;
        proxy_pass_request_headers off;
}

The problem is that nginx doesn't seems to decode the URI

/imagesproxy?uri=http%3A%2F%2Fwww.example.com%2Fwp-content%2Fuploads%2F2015%2F07%2Fportada-otra-vez-tu-667x1000.png

error.log:
[error] 16159#16159: *3602114 invalid URL prefix in
"http%3A%2F%2Fwww.alicekellen.com%2F

Any ideas?

Thank you!

Posted at Nginx Forum: https://forum.nginx.org/read.php?2,277191,277191#msg-277191