diff --git a/wp-includes/class-wp-block-type.php b/wp-includes/class-wp-block-type.php
index bd1109fb8f..ba0b59b8ad 100644
--- a/wp-includes/class-wp-block-type.php
+++ b/wp-includes/class-wp-block-type.php
@@ -32,9 +32,9 @@ class WP_Block_Type {
 
 	/**
 	 * @since 5.5.0
-	 * @var string
+	 * @var string|null
 	 */
-	public $category = '';
+	public $category = null;
 
 	/**
 	 * @since 5.5.0
@@ -44,9 +44,9 @@ class WP_Block_Type {
 
 	/**
 	 * @since 5.5.0
-	 * @var string
+	 * @var string|null
 	 */
-	public $icon = '';
+	public $icon = null;
 
 	/**
 	 * @since 5.5.0
@@ -104,25 +104,25 @@ class WP_Block_Type {
 	 * Block type editor script handle.
 	 *
 	 * @since 5.0.0
-	 * @var string
+	 * @var string|null
 	 */
-	public $editor_script = '';
+	public $editor_script = null;
 
 	/**
 	 * Block type front end script handle.
 	 *
 	 * @since 5.0.0
-	 * @var string
+	 * @var string|null
 	 */
-	public $script = '';
+	public $script = null;
 
 	/**
 	 * Block type editor style handle.
 	 *
 	 * @since 5.0.0
-	 * @var string
+	 * @var string|null
 	 */
-	public $editor_style = '';
+	public $editor_style = null;
 
 	/**
 	 * Block type front end style handle.
@@ -130,7 +130,7 @@ class WP_Block_Type {
 	 * @since 5.0.0
 	 * @var string
 	 */
-	public $style = '';
+	public $style = null;
 
 	/**
 	 * Constructor.
diff --git a/wp-includes/version.php b/wp-includes/version.php
index 3ff723458e..dfa72a9464 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -13,7 +13,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.5-alpha-47906';
+$wp_version = '5.5-alpha-47907';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.