diff --git a/src/wp-includes/customize/class-wp-customize-selective-refresh.php b/src/wp-includes/customize/class-wp-customize-selective-refresh.php
index 046b878de7..bf8a9e3c8e 100644
--- a/src/wp-includes/customize/class-wp-customize-selective-refresh.php
+++ b/src/wp-includes/customize/class-wp-customize-selective-refresh.php
@@ -12,7 +12,7 @@
  *
  * @since 4.5.0
  */
-class WP_Customize_Selective_Refresh {
+final class WP_Customize_Selective_Refresh {
 
 	/**
 	 * Query var used in requests to render partials.