diff --git a/js/ui-helper.js b/js/ui-helper.js
index cb76dde..fa0e156 100644
--- a/js/ui-helper.js
+++ b/js/ui-helper.js
@@ -4,11 +4,13 @@
   var mobileMenu = navMenu.cloneNode(true)
 
   // Clear classList of clone
-  var classes = new Array(mobileMenu.classList.length);
-  for (var i = 0, len = mobileMenu.classList.length; i < len; i++) {
-     classes[i] = mobileMenu.classList.item(i);
+  if ( mobileMenu.classList.length > 0 ) {
+    var classes = new Array(mobileMenu.classList.length)
+    for (var i = 0, len = mobileMenu.classList.length; i < len; i++) {
+       classes[i] = mobileMenu.classList.item(i)
+    }
+    mobileMenu.classList.remove(classes)
   }
-  mobileMenu.classList.remove(classes);
 
   mobileMenu.classList.add('side-nav')
   mobileMenu.setAttribute('id', 'mobile-sidebar')