diff --git a/wp-includes/customize/class-wp-customize-selective-refresh.php b/wp-includes/customize/class-wp-customize-selective-refresh.php
index 87113486b2..0b5c446131 100644
--- a/wp-includes/customize/class-wp-customize-selective-refresh.php
+++ b/wp-includes/customize/class-wp-customize-selective-refresh.php
@@ -49,7 +49,7 @@ final class WP_Customize_Selective_Refresh {
 	 * Keep track of the current partial being rendered.
 	 *
 	 * @since 4.5.0
-	 * @var string
+	 * @var string|null
 	 */
 	protected $current_partial_id;
 
diff --git a/wp-includes/version.php b/wp-includes/version.php
index ba48720fad..1caa576403 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -13,7 +13,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.3-alpha-45427';
+$wp_version = '5.3-alpha-45428';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.