diff --git a/lib/moment-duration-format.js b/lib/moment-duration-format.js
index 71fd82c..2972a96 100644
--- a/lib/moment-duration-format.js
+++ b/lib/moment-duration-format.js
@@ -1720,7 +1720,7 @@
 
     // Run feature tests for `Intl.NumberFormat#format`.
     var intlNumberFormatFormatter = function(number, locale, options) {
-        if (window.Intl && window.Intl.NumberFormat) {
+        if (window && window.Intl && window.Intl.NumberFormat) {
             return window.Intl.NumberFormat(locale, options).format(number);
         }
     };