diff --git src/wp-includes/class-wp-customize-widgets.php src/wp-includes/class-wp-customize-widgets.php
index 0aa75168a4..9779f9d65b 100644
--- src/wp-includes/class-wp-customize-widgets.php
+++ src/wp-includes/class-wp-customize-widgets.php
@@ -1217,7 +1217,7 @@ final class WP_Customize_Widgets {
 	 * @return bool Whether the widget is rendered.
 	 */
 	public function is_widget_rendered( $widget_id ) {
-		return in_array( $widget_id, $this->rendered_widgets, true );
+		return ! empty( $this->rendered_widgets[ $widget_id ] );
 	}
 
 	/**