diff --git a/src/wp-includes/class-wp-block-type.php b/src/wp-includes/class-wp-block-type.php
index ba0b59b8ad..716faf010a 100644
--- a/src/wp-includes/class-wp-block-type.php
+++ b/src/wp-includes/class-wp-block-type.php
@@ -128,7 +128,7 @@ class WP_Block_Type {
 	 * Block type front end style handle.
 	 *
 	 * @since 5.0.0
-	 * @var string
+	 * @var string|null
 	 */
 	public $style = null;