diff --git a/src/wp-includes/rest-api/endpoints/class-wp-rest-comments-controller.php b/src/wp-includes/rest-api/endpoints/class-wp-rest-comments-controller.php
index 117529d..90ca05f 100644
--- a/src/wp-includes/rest-api/endpoints/class-wp-rest-comments-controller.php
+++ b/src/wp-includes/rest-api/endpoints/class-wp-rest-comments-controller.php
@@ -1527,7 +1527,14 @@ class WP_REST_Comments_Controller extends WP_REST_Controller {
 	 * @return bool Whether post can be read.
 	 */
 	protected function check_read_post_permission( $post, $request ) {
-		$posts_controller = new WP_REST_Posts_Controller( $post->post_type );
+		$post_type = get_post_type_object( $post->post_type );
+		if ( $post_type->rest_controller_class && class_exists( $post_type->rest_controller_class ) ) {
+			$posts_controller_class = $post_type->rest_controller_class;
+		} else {
+			$posts_controller_class = 'WP_REST_Posts_Controller';
+		}
+		$posts_controller = new $posts_controller_class( $post->post_type );
+
 		$post_type = get_post_type_object( $post->post_type );
 
 		$has_password_filter = false;
diff --git a/src/wp-includes/rest-api/endpoints/class-wp-rest-revisions-controller.php b/src/wp-includes/rest-api/endpoints/class-wp-rest-revisions-controller.php
index d3f665d..1c36741 100644
--- a/src/wp-includes/rest-api/endpoints/class-wp-rest-revisions-controller.php
+++ b/src/wp-includes/rest-api/endpoints/class-wp-rest-revisions-controller.php
@@ -53,7 +53,14 @@ class WP_REST_Revisions_Controller extends WP_REST_Controller {
 	 */
 	public function __construct( $parent_post_type ) {
 		$this->parent_post_type = $parent_post_type;
-		$this->parent_controller = new WP_REST_Posts_Controller( $parent_post_type );
+		$post_type = get_post_type_object( $parent_post_type );
+		if ( $post_type->rest_controller_class && class_exists( $post_type->rest_controller_class ) ) {
+			$parent_controller_class = $post_type->rest_controller_class;
+		} else {
+			$parent_controller_class = 'WP_REST_Posts_Controller';
+		}
+		$this->parent_controller = new $parent_controller_class( $parent_post_type );
+
 		$this->namespace = 'wp/v2';
 		$this->rest_base = 'revisions';
 		$post_type_object = get_post_type_object( $parent_post_type );