diff --git src/wp-includes/taxonomy.php src/wp-includes/taxonomy.php
index 9ddd02c..72ce505 100644
--- src/wp-includes/taxonomy.php
+++ src/wp-includes/taxonomy.php
@@ -393,7 +393,7 @@ function register_taxonomy( $taxonomy, $object_type, $args = array() ) {
 	 * @param array|string $object_type Object type or array of object types.
 	 * @param array        $args        Array of taxonomy registration arguments.
 	 */
-	do_action( 'registered_taxonomy', $taxonomy, $object_type, $args );
+	do_action( 'registered_taxonomy', $taxonomy, $object_type, (array) $taxonomy_object );
 }
 
 /**