diff --git a/core/lib/Drupal/Core/Cache/Context/QueryArgsCacheContext.php b/core/lib/Drupal/Core/Cache/Context/QueryArgsCacheContext.php
index d2cce4c..1994f76 100644
--- a/core/lib/Drupal/Core/Cache/Context/QueryArgsCacheContext.php
+++ b/core/lib/Drupal/Core/Cache/Context/QueryArgsCacheContext.php
@@ -25,16 +25,20 @@ public static function getLabel() {
    */
   public function getContext($query_arg = NULL) {
     if ($query_arg === NULL) {
+      // All arguments requested. Use normalized query string to minimize
+      // variations.
       $value = $this->requestStack->getCurrentRequest()->getQueryString();
       return ($value !== NULL) ? $value : '';
     }
-    elseif ($this->requestStack->getCurrentRequest()->query->has($query_arg)) {
+    if ($this->requestStack->getCurrentRequest()->query->has($query_arg)) {
+      // Requested header exists in request.
       $value = $this->requestStack->getCurrentRequest()->query->get($query_arg);
       if ($value !== '') {
         return $value;
       }
       return '?valueless?';
     }
+    // No header in request.
     return '';
   }