diff --git a/core/modules/serialization/src/Normalizer/EntityNormalizer.php b/core/modules/serialization/src/Normalizer/EntityNormalizer.php
index 972786aeb4..b3a881e02f 100644
--- a/core/modules/serialization/src/Normalizer/EntityNormalizer.php
+++ b/core/modules/serialization/src/Normalizer/EntityNormalizer.php
@@ -61,13 +61,13 @@ public function denormalize($data, $class, $format = NULL, array $context = [])
         // uuid). If the incoming field data is set to an empty array, this will
         // also have the effect of emptying the field in REST module.
         $field_item_list->setValue([]);
+        $field_item_list_class = get_class($field_item_list);
 
         if ($field_data) {
-          // The field instance must be passed in the context so that denormalizer
-          // can update field values. The entity itself does not need to be passed
-          // because nothing except the current field needs to be set.
-          $context['__target_field_instance'] = $field_item_list;
-          $this->serializer->denormalize($field_data, get_class($field_item_list), $format, $context);
+          // The field instance must be passed in the context so that the field
+          // denormalizer can update field values for the parent entity.
+          $context['target_instance'] = $field_item_list;
+          $this->serializer->denormalize($field_data, $field_item_list_class, $format, $context);
         }
       }
     }
@@ -156,7 +156,7 @@ protected function extractBundleData(array &$data, EntityTypeInterface $entity_t
 
     // Make sure the submitted bundle is a valid bundle for the entity type.
     if ($bundle_types && !in_array($bundle_value, $bundle_types)) {
-      throw new UnexpectedValueException(sprintf('"%s" is not a valid bundle type for denormalization.', $data[$bundle_key]));
+      throw new UnexpectedValueException(sprintf('"%s" is not a valid bundle type for denormalization.', $bundle_value));
     }
 
     return [$bundle_key => $bundle_value];
diff --git a/core/modules/serialization/src/Normalizer/FieldItemNormalizer.php b/core/modules/serialization/src/Normalizer/FieldItemNormalizer.php
index b486f9e3cb..a3cfcf206f 100644
--- a/core/modules/serialization/src/Normalizer/FieldItemNormalizer.php
+++ b/core/modules/serialization/src/Normalizer/FieldItemNormalizer.php
@@ -2,6 +2,7 @@
 
 namespace Drupal\serialization\Normalizer;
 
+use Drupal\Core\Field\FieldItemInterface;
 use Symfony\Component\Serializer\Exception\InvalidArgumentException;
 use Symfony\Component\Serializer\Normalizer\DenormalizerInterface;
 
@@ -13,18 +14,22 @@ class FieldItemNormalizer extends ComplexDataNormalizer implements DenormalizerI
   /**
    * {@inheritdoc}
    */
-  protected $supportedInterfaceOrClass = 'Drupal\Core\Field\FieldItemInterface';
+  protected $supportedInterfaceOrClass = FieldItemInterface::class;
 
   /**
    * {@inheritdoc}
    */
   public function denormalize($data, $class, $format = NULL, array $context = array()) {
-    if (!isset($context['__target_field_item_instance'])) {
-      throw new InvalidArgumentException('$context[\'__target_field_item_instance\'] must be set to denormalize with the FieldItemNormalizer');
+    if (!isset($context['target_instance'])) {
+      throw new InvalidArgumentException('$context[\'target_instance\'] must be set to denormalize with the FieldItemNormalizer');
+    }
+
+    if ($context['target_instance']->getParent() == NULL) {
+      throw new InvalidArgumentException('The field item passed in via $context[\'target_instance\'] must have a parent set.');
     }
 
     /** @var \Drupal\Core\Field\FieldItemInterface $field_item */
-    $field_item = $context['__target_field_item_instance'];
+    $field_item = $context['target_instance'];
 
     $field_item->setValue($this->constructValue($data, $context));
     return $field_item;
diff --git a/core/modules/serialization/src/Normalizer/FieldNormalizer.php b/core/modules/serialization/src/Normalizer/FieldNormalizer.php
index 78b28a9b49..1847379b23 100644
--- a/core/modules/serialization/src/Normalizer/FieldNormalizer.php
+++ b/core/modules/serialization/src/Normalizer/FieldNormalizer.php
@@ -26,19 +26,19 @@ class FieldNormalizer extends ListNormalizer implements DenormalizerInterface {
    * {@inheritdoc}
    */
   public function denormalize($data, $class, $format = NULL, array $context = array()) {
-    if (!isset($context['__target_field_instance'])) {
-      throw new InvalidArgumentException('$context[\'__target_field_instance\'] must be set to denormalize with the FieldNormalizer');
+    if (!isset($context['target_instance'])) {
+      throw new InvalidArgumentException('$context[\'target_instance\'] must be set to denormalize with the FieldNormalizer');
     }
 
     /** @var FieldItemListInterface $items */
-    $items = $context['__target_field_instance'];
+    $items = $context['target_instance'];
     $item_class = $items->getItemDefinition()->getClass();
     foreach ($data as $item_data) {
       // Create a new item and pass it as the target for the unserialization of
       // $item_data. All items in field should have removed before this method
       // was called.
       // @see \Drupal\serialization\Normalizer\ContentEntityNormalizer::denormalize().
-      $context['__target_field_item_instance'] = $items->appendItem();
+      $context['target_instance'] = $items->appendItem();
       $this->serializer->denormalize($item_data, $item_class, $format, $context);
     }
     return $items;