diff --git a/extra/html-extra/HtmlExtension.php b/extra/html-extra/HtmlExtension.php
index 41ac0c48e0..b8f5dac50d 100644
--- a/extra/html-extra/HtmlExtension.php
+++ b/extra/html-extra/HtmlExtension.php
@@ -92,7 +92,7 @@ public static function htmlClasses(...$args): string
     {
         $classes = [];
         foreach ($args as $i => $arg) {
-            if (\is_string($arg) || $arg instanceof \Stringable) {
+            if (\is_string($arg) || $arg instanceof Markup) {
                 $classes[] = (string) $arg;
             } elseif (\is_array($arg)) {
                 foreach ($arg as $class => $condition) {