Bluebird's possibly unhandled behavior

unhandled.js

var Promise = require('bluebird');

var promise1 = new Promise(function (resolve, reject) {
  reject(new Error('I will be flagged as possibly unhandled'));
});

var promise2 = new Promise(function (resolve, reject) {
  reject(new Error('I will not be flagged'));
});

setImmediate(function () {
  promise1.catch(function (err) {
    console.log('Caught:', err);
  });
});

promise2.catch(function (err) {
  console.log('Caught:', err);
});