diff --git a/wp-includes/class-wp-theme-json.php b/wp-includes/class-wp-theme-json.php
index e482799f4f..f4442471e1 100644
--- a/wp-includes/class-wp-theme-json.php
+++ b/wp-includes/class-wp-theme-json.php
@@ -1313,7 +1313,7 @@ class WP_Theme_JSON {
 						continue;
 					}
 
-					$class_name    = sanitize_title( _wp_array_get( $layout_definition, array( 'className' ), false ) );
+					$class_name    = _wp_array_get( $layout_definition, array( 'className' ), false );
 					$spacing_rules = _wp_array_get( $layout_definition, array( 'spacingStyles' ), array() );
 
 					if (
@@ -1370,7 +1370,7 @@ class WP_Theme_JSON {
 		) {
 			$valid_display_modes = array( 'block', 'flex', 'grid' );
 			foreach ( $layout_definitions as $layout_definition ) {
-				$class_name       = sanitize_title( _wp_array_get( $layout_definition, array( 'className' ), false ) );
+				$class_name       = _wp_array_get( $layout_definition, array( 'className' ), false );
 				$base_style_rules = _wp_array_get( $layout_definition, array( 'baseStyles' ), array() );
 
 				if (
@@ -1567,6 +1567,9 @@ class WP_Theme_JSON {
 
 		$stylesheet = '';
 		foreach ( static::PRESETS_METADATA as $preset_metadata ) {
+			if ( empty( $preset_metadata['classes'] ) ) {
+				continue;
+			}
 			$slugs = static::get_settings_slugs( $settings, $preset_metadata, $origins );
 			foreach ( $preset_metadata['classes'] as $class => $property ) {
 				foreach ( $slugs as $slug ) {
@@ -1764,6 +1767,9 @@ class WP_Theme_JSON {
 	protected static function compute_preset_vars( $settings, $origins ) {
 		$declarations = array();
 		foreach ( static::PRESETS_METADATA as $preset_metadata ) {
+			if ( empty( $preset_metadata['css_vars'] ) ) {
+				continue;
+			}
 			$values_by_slug = static::get_settings_values_by_slug( $settings, $preset_metadata, $origins );
 			foreach ( $values_by_slug as $slug => $value ) {
 				$declarations[] = array(
diff --git a/wp-includes/version.php b/wp-includes/version.php
index a19fb27f3c..3d24c8f562 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -16,7 +16,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '6.4-alpha-56544';
+$wp_version = '6.4-alpha-56545';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.