proxy_ssl_trusted_certificate contains dummy certificate

Hi,

I use the following nginx configuration to proxy traffic to upstream hosts:

*** nginx.conf; location level
proxy_ssl_trusted_certificate trusted.pem;
proxy_pass https://host:443;

When my 'trusted.pem' contains correct certificates meaning the root-ca and intermediate-ca nginx proxies the traffic accordingly, but this is also the case when my 'trusted.pem' contains dummy certificates.

Can somebody explain this?

Regards,