"Error: gapi.client.storage is undefined"

var apiKey = 'MY API KEY';
var projectId = 'MY PROJECT ID FROM GOOGLE STORAGE';
var clientId = 'MY CLIENT ID FROM GOOGLE STORAGE'

googleCloudService.handleClientLoad(apiKey);
googleCloudService.initializeApi('v1');
googleCloudService.listBuckets(projectId); // <- Throws the Console Errror

/**
 * Set required API keys and check authentication status.
 */
this.handleClientLoad = function(apiKey) {
  gapi.client.setApiKey(apiKey);
};

/**
 * Load the Google Cloud Storage API.
 */
this.initializeApi = function(apiVersion){
  gapi.client.load('storage', apiVersion).then(function success(res) {
      console.log('loaded storage api');
    },
    function error(res) {
      return alert('Error loading storage api: ' + JSON.stringify(res)); // throw error
    });
};

/**
 * Google Cloud Storage API request to retrieve the list of buckets in
 * your Google Cloud Storage project.
 */
this.listBuckets = function(projectId) {
  var request = gapi.client.storage.buckets.list({  // <-- ERROR
    'project': projectId
  });
  console.log(request);
};