diff --git a/core/lib/Drupal/Core/Template/Attribute.php b/core/lib/Drupal/Core/Template/Attribute.php
index f42ee32..85066e2 100644
--- a/core/lib/Drupal/Core/Template/Attribute.php
+++ b/core/lib/Drupal/Core/Template/Attribute.php
@@ -161,12 +161,12 @@ public function addClass() {
   }
 
   /**
-   * Adds attribute or merges values on to array of existing attribute values.
+   * Sets values for an attribute key.
    *
    * @param string $attribute
    *   Name of the attribute.
    * @param string|array $value
-   *   Value(s) to add or merge to the given attribute.
+   *   Value(s) to set for the given attribute key.
    *
    * @return $this
    */