diff --git a/core/lib/Drupal/Core/Cache/Cache.php b/core/lib/Drupal/Core/Cache/Cache.php
index b5508a1..a5e1697 100644
--- a/core/lib/Drupal/Core/Cache/Cache.php
+++ b/core/lib/Drupal/Core/Cache/Cache.php
@@ -22,6 +22,14 @@ class Cache {
   const PERMANENT = CacheBackendInterface::CACHE_PERMANENT;
 
   /**
+   *
+   * Contains the valid cache contexts, pulled from the container.
+   *
+   * @var \Drupal\Core\Cache\CacheContextInterface[]
+   */
+  protected static $validCacheContexts;
+
+  /**
    * Merges arrays of cache contexts and removes duplicates.
    *
    * @param string[] …
@@ -62,9 +70,8 @@ public static function validateContexts(array $context_tokens) {
     // The set of existing (thus valid) cache contexts is stored on the
     // container; it's safe to statically cache this because it cannot change
     // during the request.
-    static $valid_contexts;
-    if (!isset($valid_contexts)) {
-      $valid_contexts = \Drupal::getContainer()->getParameter('cache_contexts');
+    if (!isset(static::$validCacheContexts)) {
+      static::$validCacheContexts = \Drupal::getContainer()->getParameter('cache_contexts');
     }
 
     foreach ($context_tokens as $value) {
@@ -76,7 +83,7 @@ public static function validateContexts(array $context_tokens) {
       if (strpos($value, ':') !== FALSE) {
         $value = substr($value, 0, strpos($value, ':'));
       }
-      if (!in_array($value, $valid_contexts)) {
+      if (!in_array($value, static::$validCacheContexts)) {
         throw new \LogicException('"' . $value. '" is not a valid cache context ID.');
       }
     }