diff --git a/core/lib/Drupal/Core/Session/MetadataBag.php b/core/lib/Drupal/Core/Session/MetadataBag.php
index efb4983..d4fcf83 100644
--- a/core/lib/Drupal/Core/Session/MetadataBag.php
+++ b/core/lib/Drupal/Core/Session/MetadataBag.php
@@ -35,7 +35,7 @@ public function __construct(Settings $settings) {
    *   The per-session CSRF token seed.
    */
   public function setCsrfTokenSeed($csrf_token_seed) {
-    $this->meta[self::CSRF_TOKEN_SEED] = $csrf_token_seed;
+    $this->meta[static::CSRF_TOKEN_SEED] = $csrf_token_seed;
   }
 
   /**
@@ -45,8 +45,8 @@ public function setCsrfTokenSeed($csrf_token_seed) {
    *   The per-session CSRF token seed or null when no value is set.
    */
   public function getCsrfTokenSeed() {
-    if (isset($this->meta[self::CSRF_TOKEN_SEED])) {
-      return $this->meta[self::CSRF_TOKEN_SEED];
+    if (isset($this->meta[static::CSRF_TOKEN_SEED])) {
+      return $this->meta[static::CSRF_TOKEN_SEED];
     }
   }
 
@@ -54,7 +54,7 @@ public function getCsrfTokenSeed() {
    * Clear the CSRF token seed.
    */
   public function clearCsrfTokenSeed() {
-    unset($this->meta[self::CSRF_TOKEN_SEED]);
+    unset($this->meta[static::CSRF_TOKEN_SEED]);
   }
 
 }