diff --git a/core/lib/Drupal/Core/Config/CachedStorage.php b/core/lib/Drupal/Core/Config/CachedStorage.php
index 7253b54..81b2660 100644
--- a/core/lib/Drupal/Core/Config/CachedStorage.php
+++ b/core/lib/Drupal/Core/Config/CachedStorage.php
@@ -107,8 +107,8 @@ public function readMultiple(array $names) {
     }
 
     // Add the configuration objects from the cache to the list.
-    foreach ($cached_list as $name => $cache) {
-      $list[$name] = $cache->data;
+    foreach ($cached_list as $cid => $cache) {
+      $list[$this->getNameFromCacheKey($cid)] = $cache->data;
     }
 
     // Ensure that only existing configuration objects are returned, filter out
@@ -276,6 +276,19 @@ protected function getCacheKeys(array $names) {
   }
 
   /**
+   * Returns the config name from a cache key.
+   *
+   * @param string $cid
+   *   Cache key
+   *
+   * @return string
+   *   Name of the config file.
+   */
+  protected function getNameFromCacheKey($cid) {
+    return $this->cachePrefix ? substr($cid, strlen($this->cachePrefix) + 1) : $cid;
+  }
+
+  /**
    * Set the cache prefix used by this storage.
    *
    * @param string $cachePrefix