diff --git a/lib/short.js b/lib/short.js
index 1520916..328d7de 100644
--- a/lib/short.js
+++ b/lib/short.js
@@ -147,6 +147,7 @@ exports.list = function() {
  */
 
 var extend = function(original, updates) {
+  original = original || {};
   Object.keys(updates).forEach(function(key) {
     original[key] = updates[key];
   });