diff --git a/core/lib/Drupal/Component/Render/MarkupInterface.php b/core/lib/Drupal/Component/Render/MarkupInterface.php
index 41c4f3adb1..8c4f50b60d 100644
--- a/core/lib/Drupal/Component/Render/MarkupInterface.php
+++ b/core/lib/Drupal/Component/Render/MarkupInterface.php
@@ -39,14 +39,4 @@ interface MarkupInterface extends \JsonSerializable, \Countable {
    */
   public function __toString();
 
-  /**
-   * Returns the length of the string emitted by __toString().
-   *
-   * Twig uses the \Countable interface to determine if an object is empty.
-   *
-   * @return int
-   *   The length of the string.
-   */
-  public function count();
-
 }
diff --git a/core/lib/Drupal/Core/Template/Attribute.php b/core/lib/Drupal/Core/Template/Attribute.php
index 6cf08dbb37..ddb29a3b2a 100644
--- a/core/lib/Drupal/Core/Template/Attribute.php
+++ b/core/lib/Drupal/Core/Template/Attribute.php
@@ -332,6 +332,7 @@ public function __toString() {
   /**
    * {@inheritdoc}
    */
+  #[\ReturnTypeWillChange]
   public function count() {
     return count($this->__toString());
   }