diff --git a/src/wp-includes/class-wp-icons-registry.php b/src/wp-includes/class-wp-icons-registry.php
index 32c4ad83bc396..2e306bec77e53 100644
--- a/src/wp-includes/class-wp-icons-registry.php
+++ b/src/wp-includes/class-wp-icons-registry.php
@@ -18,7 +18,7 @@ class WP_Icons_Registry {
 	 *
 	 * @var array[]
 	 */
-	private $registered_icons = array();
+	protected $registered_icons = array();
 
 
 	/**
@@ -26,12 +26,12 @@ class WP_Icons_Registry {
 	 *
 	 * @var WP_Icons_Registry|null
 	 */
-	private static $instance = null;
+	protected static $instance = null;
 
 	/**
 	 * Constructor.
 	 *
-	 * WP_Icons_Registry is a singleton class, so keep this private.
+	 * WP_Icons_Registry is a singleton class, so keep this protected.
 	 *
 	 * For 7.0, the Icons Registry is closed for third-party icon registry,
 	 * serving only a subset of core icons.
@@ -40,7 +40,7 @@ class WP_Icons_Registry {
 	 * SVG files and as entries in a single manifest file. On init, the
 	 * registry is loaded with those icons listed in the manifest.
 	 */
-	private function __construct() {
+	protected function __construct() {
 		$icons_directory = __DIR__ . '/icons/';
 		$icons_directory = trailingslashit( $icons_directory );
 		$manifest_path   = $icons_directory . 'manifest.php';
@@ -101,7 +101,7 @@ private function __construct() {
 	 * }
 	 * @return bool True if the icon was registered with success and false otherwise.
 	 */
-	private function register( $icon_name, $icon_properties ) {
+	protected function register( $icon_name, $icon_properties ) {
 		if ( ! isset( $icon_name ) || ! is_string( $icon_name ) ) {
 			_doing_it_wrong(
 				__METHOD__,
@@ -188,7 +188,7 @@ private function register( $icon_name, $icon_properties ) {
 	 * @param string $icon_content The icon SVG content to sanitize.
 	 * @return string The sanitized icon SVG content.
 	 */
-	private function sanitize_icon_content( $icon_content ) {
+	protected function sanitize_icon_content( $icon_content ) {
 		$allowed_tags = array(
 			'svg'     => array(
 				'class'       => true,
@@ -223,7 +223,7 @@ private function sanitize_icon_content( $icon_content ) {
 	 * @param string $icon_name Icon name including namespace.
 	 * @return string|null The content of the icon, if found.
 	 */
-	private function get_content( $icon_name ) {
+	protected function get_content( $icon_name ) {
 		if ( ! isset( $this->registered_icons[ $icon_name ]['content'] ) ) {
 			$content = file_get_contents(
 				$this->registered_icons[ $icon_name ]['filePath']