Connecting to postgres on Heroku with Node.js

I try to connect to my postgres database on Heroku by:

var pg = require('pg');
pg.defaults.ssl = true;
var pool = new pg.Pool(process.env.DATABASE_URL);

pool.connect(function(err, client, done) {
if(err) {
  return console.error('error fetching client from pool', err);
}

I have confirmed the value of proccess.env.DATABASE_URL it has the right format, and I can successfully connect to it via psql postgres://XXXXXXXX:[email protected]:5432/XXXXXXXX

This is the output, and what confuses me is the 127.0.0.1 reference if this output.

2016-06-27T14:58:52.714154+00:00 app[web.1]: Express server listening on port 18119
2016-06-27T14:59:29.175122+00:00 app[web.1]: error fetching client from pool { Error: connect ECONNREFUSED 127.0.0.1:5432
2016-06-27T14:59:29.175133+00:00 app[web.1]:     at Object.exports._errnoException (util.js:949:11)
2016-06-27T14:59:29.175134+00:00 app[web.1]:     at exports._exceptionWithHostPort (util.js:972:20)
2016-06-27T14:59:29.175135+00:00 app[web.1]:     at TCPConnectWrap.afterConnect [as oncomplete] (net.js:1080:14)
2016-06-27T14:59:29.175136+00:00 app[web.1]:   code: 'ECONNREFUSED',
2016-06-27T14:59:29.175137+00:00 app[web.1]:   errno: 'ECONNREFUSED',
2016-06-27T14:59:29.175137+00:00 app[web.1]:   syscall: 'connect',
2016-06-27T14:59:29.175138+00:00 app[web.1]:   address: '127.0.0.1',
2016-06-27T14:59:29.175139+00:00 app[web.1]:   port: 5432 }