diff --git a/wp-includes/class-wp-post-type.php b/wp-includes/class-wp-post-type.php
index 0099515050..bb148067c0 100644
--- a/wp-includes/class-wp-post-type.php
+++ b/wp-includes/class-wp-post-type.php
@@ -343,7 +343,7 @@ final class WP_Post_Type {
 	 * @since 5.3.0
 	 * @var WP_REST_Controller $rest_controller
 	 */
-	private $rest_controller;
+	public $rest_controller;
 
 	/**
 	 * Constructor.
@@ -722,6 +722,10 @@ final class WP_Post_Type {
 			$this->rest_controller = new $class( $this->name );
 		}
 
+		if ( ! ( $this->rest_controller instanceof $class ) ) {
+			return null;
+		}
+
 		return $this->rest_controller;
 	}
 }
diff --git a/wp-includes/rest-api/endpoints/class-wp-rest-posts-controller.php b/wp-includes/rest-api/endpoints/class-wp-rest-posts-controller.php
index 4a00336e34..2b71a76cb0 100644
--- a/wp-includes/rest-api/endpoints/class-wp-rest-posts-controller.php
+++ b/wp-includes/rest-api/endpoints/class-wp-rest-posts-controller.php
@@ -15,15 +15,6 @@
  * @see WP_REST_Controller
  */
 class WP_REST_Posts_Controller extends WP_REST_Controller {
-
-	/**
-	 * Instances of post type controllers keyed by post type.
-	 *
-	 * @since 5.3.0
-	 * @var WP_REST_Controller[]
-	 */
-	private static $post_type_controllers = array();
-
 	/**
 	 * Post type.
 	 *
diff --git a/wp-includes/version.php b/wp-includes/version.php
index e3146c9539..3cfbb17022 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -13,7 +13,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.3-beta2-46434';
+$wp_version = '5.3-beta2-46435';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.