diff --git a/code/extensions/GridFieldSortableObject.php b/code/extensions/GridFieldSortableObject.php
index 7e1e425..61b643c 100644
--- a/code/extensions/GridFieldSortableObject.php
+++ b/code/extensions/GridFieldSortableObject.php
@@ -63,7 +63,7 @@ class GridFieldSortableObject extends DataExtension {
      * @param {string} $className Name of the DataObject to check
      */
     public static function is_sortable_class($className) {
-        if(in_array($classname, self::$sortable_classes)) {
+        if(in_array($className, self::$sortable_classes)) {
             return true;
         }