diff --git a/src/wp-includes/html-api/class-wp-html-tag-processor.php b/src/wp-includes/html-api/class-wp-html-tag-processor.php
index debc87321c..2e84b3d719 100644
--- a/src/wp-includes/html-api/class-wp-html-tag-processor.php
+++ b/src/wp-includes/html-api/class-wp-html-tag-processor.php
@@ -1743,7 +1743,7 @@ class WP_HTML_Tag_Processor {
 	 * @param string $prefix Prefix of requested attribute names.
 	 * @return array|null List of attribute names, or `null` when no tag opener is matched.
 	 */
-	function get_attribute_names_with_prefix( $prefix ) {
+	public function get_attribute_names_with_prefix( $prefix ) {
 		if ( $this->is_closing_tag || null === $this->tag_name_starts_at ) {
 			return null;
 		}