node https get request to public api results in Error: CERT_UNTRUSTED

trying to perform a simple https request to a public api but i'm getting "Error: CERT_UNTRUSTED"

require('https');

var options = {
  host: 'btc-e.com',
  path: '/api/2/btc_usd/ticker',
  port: '443',
  method: 'GET',
  headers: {accept:'*/*'}
};

var req = https.get(options, function(res) {
 console.log(res.statusCode);
 res.on('data', function(d) {
    process.stdout.write(d);
 });
});

req.on('error', function(e) {
  console.error(e);
});