diff --git a/core/lib/Drupal/Core/KeyValueStore/State.php b/core/lib/Drupal/Core/KeyValueStore/State.php
index f255e51..36a7973 100644
--- a/core/lib/Drupal/Core/KeyValueStore/State.php
+++ b/core/lib/Drupal/Core/KeyValueStore/State.php
@@ -56,6 +56,8 @@ public function getMultiple(array $keys) {
     if ($load) {
       $loaded_values = $this->keyValueStore->getMultiple($load);
       foreach ($load as $key) {
+        // If we find a value, even one that is NULL, add it to the cache and
+        // return it.
         if (isset($loaded_values[$key]) || array_key_exists($key, $loaded_values)) {
           $values[$key] = $loaded_values[$key];
           $this->cache[$key] = $loaded_values[$key];
@@ -91,9 +93,9 @@ public function deleteMultiple(array $keys) {
   /**
    * {@inheritdoc}
    */
-  public function get($key) {
+  public function get($key, $default = NULL) {
     $values = $this->getMultiple(array($key));
-    return isset($values[$key]) ? $values[$key] : NULL;
+    return isset($values[$key]) ? $values[$key] : $default;
   }
 
   /**
@@ -103,7 +105,7 @@ public function setMultiple(array $data) {
     foreach ($data as $key => $value) {
       $this->cache[$key] = $value;
     }
-    $this->setMultiple($data);
+    $this->keyValueStore->setMultiple($data);
   }
 
   /**
diff --git a/core/lib/Drupal/Core/KeyValueStore/StateInterface.php b/core/lib/Drupal/Core/KeyValueStore/StateInterface.php
index 9e248d8..7584abc 100644
--- a/core/lib/Drupal/Core/KeyValueStore/StateInterface.php
+++ b/core/lib/Drupal/Core/KeyValueStore/StateInterface.php
@@ -17,11 +17,13 @@
    *
    * @param string $key
    *   The key of the data to retrieve.
+   * @param mixed $default
+   *   The default value to use if the key is not found.
    *
    * @return mixed
    *   The stored value, or NULL if no value exists.
    */
-  public function get($key);
+  public function get($key, $default = NULL);
 
   /**
    * Returns the stored key/value pairs for a given set of keys.