diff --git a/lib/javascript-static.js b/lib/javascript-static.js
index caec82b2016..916220b3a98 100644
--- a/lib/javascript-static.js
+++ b/lib/javascript-static.js
@@ -262,7 +262,7 @@ function showAdvancedOnClick(button, hidetext, showtext){
     }
     var formelements = button.form.elements;
     for (var i in formelements){
-        if (formelements[i].name=='mform_showadvanced'){
+        if (formelements[i] && formelements[i].name && (formelements[i].name=='mform_showadvanced')){
             formelements[i].value = buttontext;
         }
     }