nginx invalid number of arguments in "ssl_trusted_certificate"

I am going through part 4 of the Getting Started with NGINX at https://www.linode.com/docs/web-servers/nginx/tls-deployment-best-practices-for-nginx/. For "OCSP Stapling", I added:

ssl_stapling on;
ssl_stapling_verify on;
ssl_trusted_certificate /etc/letsencrypt/live/MYDOMAIN.COM/chain.pem

(According to some other websites, I should be pointing ssl_trusted_certificate to the location of chain.pem if I had obtained my SSL certificates from LetsEncrypt.)

I tested my nginx configuration with:

nginx -t

And I got the error:

nginx: [emerg] invalid number of arguments in "ssl_trusted_certificate" directive in /etc/nginx/nginx.conf

I don't know what argument is missing. According to the documentation, the only argument is the filepath to the chain.pem file.

Any ideas how to resolve this?