diff --git a/src/misc/duo.js b/src/misc/duo.js
index 8b712dcf25..bb0f58a787 100644
--- a/src/misc/duo.js
+++ b/src/misc/duo.js
@@ -3,16 +3,28 @@
  * Copyright 2017, Duo Security
  */
 
-var Duo;
 (function (root, factory) {
-    // Browser globals (root is window)
-    var d = factory();
-    // If the Javascript was loaded via a script tag, attempt to autoload
-    // the frame.
-    d._onReady(d.init);
-    // Attach Duo to the `window` object
-    root.Duo = Duo = d;
-}(window, function () {
+    /*eslint-disable */
+    if (typeof define === 'function' && define.amd) {
+        // AMD. Register as an anonymous module.
+        define([], factory);
+    /*eslint-enable */
+    } else if (typeof module === 'object' && module.exports) {
+        // Node. Does not work with strict CommonJS, but
+        // only CommonJS-like environments that support module.exports,
+        // like Node.
+        module.exports = factory();
+    } else {
+        // Browser globals (root is window)
+        var Duo = factory();
+        // If the Javascript was loaded via a script tag, attempt to autoload
+        // the frame.
+        Duo._onReady(Duo.init);
+
+        // Attach Duo to the `window` object
+        root.Duo = Duo;
+  }
+}(this, function() {
     var DUO_MESSAGE_FORMAT = /^(?:AUTH|ENROLL)+\|[A-Za-z0-9\+\/=]+\|[A-Za-z0-9\+\/=]+$/;
     var DUO_ERROR_FORMAT = /^ERR\|[\w\s\.\(\)]+$/;
     var DUO_OPEN_WINDOW_FORMAT = /^DUO_OPEN_WINDOW\|/;
@@ -311,10 +323,10 @@ var Duo;
         }
 
         for (var i = 0; i < VALID_OPEN_WINDOW_DOMAINS.length; i++) {
-            if (parser.hostname.endsWith("." + VALID_OPEN_WINDOW_DOMAINS[i]) ||
-                parser.hostname === VALID_OPEN_WINDOW_DOMAINS[i]) {
-                return true;
-            }
+           if (parser.hostname.endsWith("." + VALID_OPEN_WINDOW_DOMAINS[i]) ||
+                   parser.hostname === VALID_OPEN_WINDOW_DOMAINS[i]) {
+               return true;
+           }
         }
         return false;
     }