Invalid Host header not being rejected by nginx

Question

I'm running a Django-powered site, and I'm seeing errors like these in my Django application's error logs:

django.core.exceptions.DisallowedHost: Invalid HTTP_HOST header: 'badhost.com'. You may need to add 'badhost.com' to ALLOWED_HOSTS.

I was under the impression that my nginx configuration, shown below (and trimmed for brevity), would prevent these requests from ever making it to the Django app; specifically, the last server block in the config. What do I have wrong?

My end-goal is for nginx to reject requests that have an invalid Host header. Maybe there's a way to filter out these error messages in my application error log?

server {
        server_name mysite.com www.mysite.com;
        listen 80;
        return 302 https://$host$request_uri;
}

server {
        server_name mysite.com www.mysite.com;
        root /home/myuser/mysite.com/public/;

        location / {
                try_files $uri @proxy_to_app;
        }

        location @proxy_to_app {
                proxy_pass http://localhost:8001;
                proxy_set_header Host $host;
                proxy_set_header X-Forwarded-For $remote_addr;
        }

        listen 443 ssl; # managed by Certbot
        ssl_certificate /etc/letsencrypt/live/mysite.com/fullchain.pem; # managed by Certbot
        ssl_certificate_key /etc/letsencrypt/live/mysite.com/privkey.pem; # managed by Certbot
}

server {
        listen 80 default_server;
        listen 443 ssl default_server;
        ssl_certificate /etc/letsencrypt/live/mysite.com/fullchain.pem; # managed by Certbot
        ssl_certificate_key /etc/letsencrypt/live/mysite.com/privkey.pem; # managed by Certbot
        return 444;
}