diff --git a/lib/ical/helpers.js b/lib/ical/helpers.js
index b4fdb94f..71860bf0 100644
--- a/lib/ical/helpers.js
+++ b/lib/ical/helpers.js
@@ -4,10 +4,10 @@
  * Portions Copyright (C) Philipp Kewisch, 2011-2015 */
 
 
-if ('noModule' in HTMLScriptElement.prototype) {
-  // In case ical.js is executed in a JavaScript module, strict mode is enabled
-  // and requires a global variable to be assigned explicitly to e.g. the window
-  // object.
+if (typeof window !== 'undefined' && 'noModule' in HTMLScriptElement.prototype) {
+  // In case ical.js is executed in the browser and a JavaScript module, strict
+  // mode is enabled and requires a global variable to be assigned explicitly
+  // to e.g. the window object.
   window.ICAL = {};
 }