diff --git a/core/modules/hal/src/Normalizer/ContentEntityNormalizer.php b/core/modules/hal/src/Normalizer/ContentEntityNormalizer.php
index c034ade..50b591d 100644
--- a/core/modules/hal/src/Normalizer/ContentEntityNormalizer.php
+++ b/core/modules/hal/src/Normalizer/ContentEntityNormalizer.php
@@ -90,11 +90,12 @@ public function normalize($entity, $format = NULL, array $context = array()) {
     // Ignore the entity ID and revision ID.
     $exclude = array($entity->getEntityType()->getKey('id'), $entity->getEntityType()->getKey('revision'));
     foreach ($fields as $field) {
-      $field_name = $field->getFieldDefinition()->getName();
+      $definition = $field->getFieldDefinition();
+      $field_name = $definition->getName();
       if (in_array($field_name, $exclude)) {
         continue;
       }
-      if (($definition = $field->getFieldDefinition()) && $definition->getType() == 'password') {
+      if ($definition->getType() == 'password') {
         // Never normalize password items.
         continue;
       }
diff --git a/core/modules/serialization/src/Normalizer/ComplexDataNormalizer.php b/core/modules/serialization/src/Normalizer/ComplexDataNormalizer.php
index 154412b..07803ff 100644
--- a/core/modules/serialization/src/Normalizer/ComplexDataNormalizer.php
+++ b/core/modules/serialization/src/Normalizer/ComplexDataNormalizer.php
@@ -7,7 +7,7 @@
 
 namespace Drupal\serialization\Normalizer;
 
-use Symfony\Component\Serializer\Exception\RuntimeException;
+use Drupal\Core\Field\FieldItemListInterface;
 
 /**
  * Converts the Drupal entity object structures to a normalized array.
@@ -34,7 +34,7 @@ class ComplexDataNormalizer extends NormalizerBase {
   public function normalize($object, $format = NULL, array $context = array()) {
     $attributes = array();
     foreach ($object as $name => $field) {
-      if (method_exists($field, 'getFieldDefinition') && ($definition = $field->getFieldDefinition()) && $definition->getType() == 'password') {
+      if ($field instanceof FieldItemListInterface && $field->getFieldDefinition()->getType() == 'password') {
         // Never normalize password items.
         continue;
       }
diff --git a/core/modules/serialization/src/Tests/EntitySerializationTest.php b/core/modules/serialization/src/Tests/EntitySerializationTest.php
index db0c944..9f2be3e 100644
--- a/core/modules/serialization/src/Tests/EntitySerializationTest.php
+++ b/core/modules/serialization/src/Tests/EntitySerializationTest.php
@@ -117,7 +117,7 @@ public function testNormalize() {
     ]);
     $account->save();
     $normalized = $this->serializer->normalize($account);
-    $this->assertTrue(empty($normalized['pass']));
+    $this->assertTrue(!array_key_exists('pass', $normalized));
   }
 
   /**