diff --git a/core/src/main/resources/org/apache/spark/ui/static/sorttable.js b/core/src/main/resources/org/apache/spark/ui/static/sorttable.js
index ff241470f32df..9960d5c34d1fc 100644
--- a/core/src/main/resources/org/apache/spark/ui/static/sorttable.js
+++ b/core/src/main/resources/org/apache/spark/ui/static/sorttable.js
@@ -207,8 +207,8 @@ sorttable = {
 
     hasInputs = (typeof node.getElementsByTagName == 'function') &&
                  node.getElementsByTagName('input').length;
-    
-    if (node.getAttribute("sorttable_customkey") != null) {
+
+    if (node.nodeType == 1 && node.getAttribute("sorttable_customkey") != null) {
       return node.getAttribute("sorttable_customkey");
     }
     else if (typeof node.textContent != 'undefined' && !hasInputs) {