Nginx Curl SSL error

After installing SSL on Nginx server, it worked on browser, but when i try access using curl command, i get error

# curl  https://serverok.in
curl: (60) server certificate verification failed. CAfile: /etc/ssl/certs/ca-certificates.crt CRLfile: none
More details here: http://curl.haxx.se/docs/sslcerts.html

curl performs SSL certificate verification by default, using a "bundle"
 of Certificate Authority (CA) public keys (CA certs). If the default
 bundle file isn't adequate, you can specify an alternate file
 using the --cacert option.
If this HTTPS server uses a certificate signed by a CA represented in
 the bundle, the certificate verification probably failed due to a
 problem with the certificate (it might be expired, or the name might
 not match the domain name in the URL).
If you'd like to turn off curl's verification of the certificate, use
 the -k (or --insecure) option.
# 

This is fixed by adding ca-bundle to .crt file.

The cert file should be in following format

YOUR_DOMAIN.crt
YOUR_DOMAIN.ca-bundle

This can be done with

cat YOUR_DOMAIN.crt YOUR_DOMAIN.ca-bundle > YOUR_DOMAIN.ssl

Now use YOUR_DOMAIN.ssl as your ssl certificate in nginx.

        ssl on;
        ssl_certificate /etc/ssl/YOUR_DOMAIN.ssl;
        ssl_certificate_key /etc/ssl/YOUR_DOMAIN.key;