Getting nested values in Immutable.js

According to the docs here: https://facebook.github.io/immutable-js/docs/#/Map/getIn I should be able to get the deeply nested value by providing an array for the keyPath argument. This is what I've done, however I'm getting undefined as the return value. http://jsfiddle.net/srxv4mwu/ var obj = Immutable.Map({categories: {1: 'a', 2: 'b'}}); var output = obj.getIn(['categories', 1]); alert(output);