diff --git a/src/wp-includes/class-wp-customize-manager.php b/src/wp-includes/class-wp-customize-manager.php
index d12eea0e5f326..b29d6a8bfc3c4 100644
--- a/src/wp-includes/class-wp-customize-manager.php
+++ b/src/wp-includes/class-wp-customize-manager.php
@@ -100,7 +100,7 @@ final class WP_Customize_Manager {
 	 * @since 4.5.0
 	 * @var array
 	 */
-	protected $components = array( 'widgets', 'nav_menus' );
+	protected $components = array( 'nav_menus' );
 
 	/**
 	 * Registered instances of WP_Customize_Section.
@@ -286,6 +286,11 @@ public function __construct( $args = array() ) {
 			$args['messenger_channel'] = sanitize_key( wp_unslash( $_REQUEST['customize_messenger_channel'] ) );
 		}
 
+		// Don't load 'widgets' component if a block theme is activated.
+		if ( ! wp_is_block_theme() ) {
+			$this->components[] = 'widgets';
+		}
+
 		$this->original_stylesheet = get_stylesheet();
 		$this->theme               = wp_get_theme( 0 === validate_file( $args['theme'] ) ? $args['theme'] : null );
 		$this->messenger_channel   = $args['messenger_channel'];