SNI: reset to default server if requested host was not found. Not only this is consistent with a case without SNI, but this also prevents abusing configurations that assume that the $host variable is limited to one of the configured names for a server. An example of potentially unsafe configuration: server { listen 443 ssl default_server; ... } server { listen 443; server_name example.com; location / { proxy_pass http://$host; } } Note: it is possible to negotiate "example.com" by SNI, and to request arbitrary host name that does not exist in the configuration above.