Nginx serves root of one subdomain instead of root of another subdomain - nginx

Question

I have two subdomains, app.mydomain.com and v1.api.mydomain.com, pointing to the same IP. I want app.mydomain.com to be proxied to localhost:5000 and v1.api.mydomain.com to be proxied to localhost:1337.
The following configuration does it (app.mydomain.com/... is served by localhost:5000 and v1.api.mydomain.com/... is served by localhost:1337) except for one thing: the root of v1.api.mydomain.com (with or without a trailing slash) isn't served by localhost:1337, it is served by localhost:5000 (app.mydomain.com) and therefore it doesn't display what I expect. How is this possible?
My first configuration file in sites-enabled:
server {
listen 80;
server_name app.mydomain.com;
location / {
proxy_pass http://localhost:5000/;
proxy_http_version 1.1;
proxy_set_header Upgrade $http_upgrade;
proxy_set_header Connection 'upgrade';
proxy_set_header Host $host;
proxy_cache_bypass $http_upgrade;
}
My second configuration file in site-enabled:
server {
listen 80;
server_name v1.api.mydomain.com;
location / {
proxy_pass http://localhost:1337/;
proxy_http_version 1.1;
proxy_set_header Upgrade $http_upgrade;
proxy_set_header Connection 'upgrade';
proxy_set_header Host $host;
proxy_cache_bypass $http_upgrade;
}
}
To make sure that the problem wasn't a redirection of some sort by the server running on localhost:1337, I shut it down and the problem is still there, so it really is something with my nginx configuration. Thanks for helping.