diff --git a/src/WP_CLI/Entity/RecursiveDataStructureTraverser.php b/src/WP_CLI/Entity/RecursiveDataStructureTraverser.php
index f9573b70..3d23da40 100644
--- a/src/WP_CLI/Entity/RecursiveDataStructureTraverser.php
+++ b/src/WP_CLI/Entity/RecursiveDataStructureTraverser.php
@@ -24,9 +24,9 @@ class RecursiveDataStructureTraverser {
 	/**
 	 * RecursiveDataStructureTraverser constructor.
 	 *
-	 * @param mixed $data The data to read/manipulate by reference.
-	 * @param string|int $key The key/property the data belongs to.
-	 * @param static $parent
+	 * @param mixed       $data            The data to read/manipulate by reference.
+	 * @param string|int  $key             The key/property the data belongs to.
+	 * @param static|null $parent_instance The parent instance of the traverser.
 	 */
 	public function __construct( &$data, $key = null, $parent_instance = null ) {
 		$this->data   =& $data;