diff --git a/core/lib/Drupal/Core/Cache/ChainedFastBackend.php b/core/lib/Drupal/Core/Cache/ChainedFastBackend.php
index 9f6be9d8ab..e72c400e52 100644
--- a/core/lib/Drupal/Core/Cache/ChainedFastBackend.php
+++ b/core/lib/Drupal/Core/Cache/ChainedFastBackend.php
@@ -170,6 +170,10 @@ public function getMultiple(&$cids, $allow_invalid = FALSE) {
       }
     }
 
+    foreach ($cache as $cid => $item) {
+      $item->data = unserialize($item->data);
+    }
+
     return $cache;
   }
 
@@ -177,6 +181,8 @@ public function getMultiple(&$cids, $allow_invalid = FALSE) {
    * {@inheritdoc}
    */
   public function set($cid, $data, $expire = Cache::PERMANENT, array $tags = []) {
+    $data = serialize($data);
+
     $this->consistentBackend->set($cid, $data, $expire, $tags);
     $this->markAsOutdated();
     // Don't write the cache tags to the fast backend as any cache tag
@@ -188,6 +194,10 @@ public function set($cid, $data, $expire = Cache::PERMANENT, array $tags = []) {
    * {@inheritdoc}
    */
   public function setMultiple(array $items) {
+    foreach ($items as &$item) {
+      $item['data'] = serialize($item['data']);
+    }
+
     $this->consistentBackend->setMultiple($items);
     $this->markAsOutdated();
     // Don't write the cache tags to the fast backend as any cache tag