diff --git a/core/lib/Drupal/Core/KeyValueStore/KeyValueCacheDecorator.php b/core/lib/Drupal/Core/KeyValueStore/KeyValueCacheDecorator.php
index ca0f9bd..8304fad 100644
--- a/core/lib/Drupal/Core/KeyValueStore/KeyValueCacheDecorator.php
+++ b/core/lib/Drupal/Core/KeyValueStore/KeyValueCacheDecorator.php
@@ -83,7 +83,7 @@ public function set($key, $value) {
     $this->keyValueStore->set($key, $value);
     $this->offsetSet($key, $value);
     // Immediately update the cache.
-    $this->setData(array('key' => $value));
+    $this->setData(array($key => $value));
   }
 
 }
diff --git a/core/lib/Drupal/Core/Utility/CacheArray.php b/core/lib/Drupal/Core/Utility/CacheArray.php
index 3e6c914..03deeae 100644
--- a/core/lib/Drupal/Core/Utility/CacheArray.php
+++ b/core/lib/Drupal/Core/Utility/CacheArray.php
@@ -214,7 +214,7 @@ protected function setData($data, $lock = TRUE) {
     $lock_name = $this->cid . ':' . $this->bin;
     if (!$lock || lock()->acquire($lock_name)) {
       if ($cached = cache($this->bin)->get($this->cid)) {
-        $data = $cached->data + $data;
+        $data = array_merge($cached->data, $data);
       }
       // Remove keys marked for deletion.
       foreach ($this->keysToRemove as $delete_key) {