diff -u b/core/modules/views/src/Plugin/views/display/DisplayPluginBase.php b/core/modules/views/src/Plugin/views/display/DisplayPluginBase.php
--- b/core/modules/views/src/Plugin/views/display/DisplayPluginBase.php
+++ b/core/modules/views/src/Plugin/views/display/DisplayPluginBase.php
@@ -2646,10 +2646,10 @@
    * @param string $id
    *   The id of the requested extender.
    *
-   * @return \Drupal\views\Plugin\views\display_extender\DisplayExtenderPluginBase[$id].
+   * @return \Drupal\views\Plugin\views\display_extender\DisplayExtenderPluginBase.
    */
   public function getExtender($id) {
-  	return isset($this->extenders[$id]) ? $this->extenders[$id] : NULL;
+    return isset($this->extenders[$id]) ? $this->extenders[$id] : NULL;
   }
 
   /**