diff --git a/core/modules/hal/tests/src/Functional/EntityResource/EntityTest/EntityTestHalJsonInternalPropertyNormalizerTest.php b/core/modules/hal/tests/src/Functional/EntityResource/EntityTest/EntityTestHalJsonInternalPropertyNormalizerTest.php
index 0ba00bd21f..ce02ca6b13 100644
--- a/core/modules/hal/tests/src/Functional/EntityResource/EntityTest/EntityTestHalJsonInternalPropertyNormalizerTest.php
+++ b/core/modules/hal/tests/src/Functional/EntityResource/EntityTest/EntityTestHalJsonInternalPropertyNormalizerTest.php
@@ -8,7 +8,7 @@
 use Drupal\Tests\rest\Functional\AnonResourceTestTrait;
 
 /**
- * Test that internal properties are not exposed in REST.
+ * Test that internal properties are not exposed in the 'hal_json' format.
  *
  * @group hal
  */
diff --git a/core/modules/rest/tests/src/Functional/EntityResource/EntityTest/EntityTestJsonInternalPropertyNormalizerTest.php b/core/modules/rest/tests/src/Functional/EntityResource/EntityTest/EntityTestJsonInternalPropertyNormalizerTest.php
index 9b7f1bcc91..7c64e3fdac 100644
--- a/core/modules/rest/tests/src/Functional/EntityResource/EntityTest/EntityTestJsonInternalPropertyNormalizerTest.php
+++ b/core/modules/rest/tests/src/Functional/EntityResource/EntityTest/EntityTestJsonInternalPropertyNormalizerTest.php
@@ -7,7 +7,7 @@
 use Drupal\Tests\rest\Functional\AnonResourceTestTrait;
 
 /**
- * Test that internal properties are not exposed in REST.
+ * Test that internal properties are not exposed in the 'json' format.
  *
  * @group rest
  */
diff --git a/core/modules/rest/tests/src/Functional/EntityResource/EntityTest/EntityTestResourceTestBase.php b/core/modules/rest/tests/src/Functional/EntityResource/EntityTest/EntityTestResourceTestBase.php
index da75f1064e..5ca1f7e44c 100644
--- a/core/modules/rest/tests/src/Functional/EntityResource/EntityTest/EntityTestResourceTestBase.php
+++ b/core/modules/rest/tests/src/Functional/EntityResource/EntityTest/EntityTestResourceTestBase.php
@@ -55,14 +55,15 @@ protected function setUpAuthorization($method) {
   protected function createEntity() {
     // Set flag so that internal field 'internal_string_field' is created.
     // @see \entity_test_entity_base_field_info()
-    $this->container->get('state')->set('entity_test.test_internal', TRUE);
+    $this->container->get('state')->set('entity_test.internal_field', TRUE);
     \Drupal::entityDefinitionUpdateManager()->applyUpdates();
 
     $entity_test = EntityTest::create([
       'name' => 'Llama',
       'type' => 'entity_test',
       // Set a value for the internal field to confirm that it will not be
-      // returned in normalization. @see \entity_test_entity_base_field_info().
+      // returned in normalization.
+      // @see \entity_test_entity_base_field_info().
       'internal_string_field' => [
         'value' => 'value to be internal',
       ],
diff --git a/core/modules/serialization/src/Normalizer/ContentEntityNormalizer.php b/core/modules/serialization/src/Normalizer/ContentEntityNormalizer.php
index 96ef4040ee..6ac8927df6 100644
--- a/core/modules/serialization/src/Normalizer/ContentEntityNormalizer.php
+++ b/core/modules/serialization/src/Normalizer/ContentEntityNormalizer.php
@@ -1,6 +1,7 @@
 <?php
 
 namespace Drupal\serialization\Normalizer;
+
 use Drupal\Core\TypedData\TypedDataInternalPropertiesHelper;
 
 /**
diff --git a/core/modules/serialization/src/Normalizer/TypedDataNormalizer.php b/core/modules/serialization/src/Normalizer/TypedDataNormalizer.php
index 3e7be7cf5e..60ce7d08f6 100644
--- a/core/modules/serialization/src/Normalizer/TypedDataNormalizer.php
+++ b/core/modules/serialization/src/Normalizer/TypedDataNormalizer.php
@@ -2,8 +2,6 @@
 
 namespace Drupal\serialization\Normalizer;
 
-use Drupal\Core\TypedData\PrimitiveInterface;
-
 /**
  * Converts typed data objects to arrays.
  */
@@ -20,11 +18,7 @@ class TypedDataNormalizer extends NormalizerBase {
    * {@inheritdoc}
    */
   public function normalize($object, $format = NULL, array $context = []) {
-    $value = $object->getValue();
-    if (is_object($value) && $object instanceof PrimitiveInterface) {
-      return $object->getCastedValue();
-    }
-    return $value;
+    return $object->getValue();
   }
 
 }
diff --git a/core/modules/serialization/tests/src/Unit/Normalizer/TimestampItemNormalizerTest.php b/core/modules/serialization/tests/src/Unit/Normalizer/TimestampItemNormalizerTest.php
index 8945d3f43e..c4e351424a 100644
--- a/core/modules/serialization/tests/src/Unit/Normalizer/TimestampItemNormalizerTest.php
+++ b/core/modules/serialization/tests/src/Unit/Normalizer/TimestampItemNormalizerTest.php
@@ -79,14 +79,14 @@ public function testNormalize() {
     $timestamp_item->getIterator()
       ->willReturn(new \ArrayIterator(['value' => 1478422920]));
 
-    $non_internal_property = $this->getTypedDataProperty(FALSE);
+    $value_property = $this->getTypedDataProperty(FALSE);
     $timestamp_item->getProperties(TRUE)
-      ->willReturn(['value' => $non_internal_property])
+      ->willReturn(['value' => $value_property])
       ->shouldBeCalled();
 
     $serializer_prophecy = $this->prophesize(Serializer::class);
 
-    $serializer_prophecy->normalize($non_internal_property, NULL, [])
+    $serializer_prophecy->normalize($value_property, NULL, [])
       ->willReturn(1478422920)
       ->shouldBeCalled();
 
diff --git a/core/modules/system/tests/modules/entity_test/config/schema/entity_test.data_types.schema.yml b/core/modules/system/tests/modules/entity_test/config/schema/entity_test.data_types.schema.yml
index 5c3bddf2b3..cebaf03905 100644
--- a/core/modules/system/tests/modules/entity_test/config/schema/entity_test.data_types.schema.yml
+++ b/core/modules/system/tests/modules/entity_test/config/schema/entity_test.data_types.schema.yml
@@ -1,4 +1,4 @@
-# Schema for the configuration of the internal property field type.
+# Schema for the configuration of the 'internal property test' field type.
 
 field.storage_settings.internal_property_test:
   type: field.storage_settings.string
diff --git a/core/modules/system/tests/modules/entity_test/entity_test.module b/core/modules/system/tests/modules/entity_test/entity_test.module
index e0f62cc4dc..025cb5fc2f 100644
--- a/core/modules/system/tests/modules/entity_test/entity_test.module
+++ b/core/modules/system/tests/modules/entity_test/entity_test.module
@@ -109,9 +109,9 @@ function entity_test_entity_type_alter(array &$entity_types) {
 function entity_test_entity_base_field_info(EntityTypeInterface $entity_type) {
   $fields = [];
 
-  if ($entity_type->id() === 'entity_test' && \Drupal::state()->get('entity_test.test_internal')) {
+  if ($entity_type->id() === 'entity_test' && \Drupal::state()->get('entity_test.internal_field')) {
     $fields['internal_string_field'] = BaseFieldDefinition::create('string')
-      ->setLabel('Internal')
+      ->setLabel('Internal field')
       ->setInternal(TRUE);
   }
   if ($entity_type->id() == 'entity_test_mulrev' && \Drupal::state()->get('entity_test.field_test_item')) {
diff --git a/core/modules/system/tests/modules/entity_test/src/Plugin/Field/FieldType/InternalPropertyTestFieldItem.php b/core/modules/system/tests/modules/entity_test/src/Plugin/Field/FieldType/InternalPropertyTestFieldItem.php
index b981339efa..2bc8154cf9 100644
--- a/core/modules/system/tests/modules/entity_test/src/Plugin/Field/FieldType/InternalPropertyTestFieldItem.php
+++ b/core/modules/system/tests/modules/entity_test/src/Plugin/Field/FieldType/InternalPropertyTestFieldItem.php
@@ -30,13 +30,13 @@ public static function propertyDefinitions(FieldStorageDefinitionInterface $fiel
 
     // Add a computed property that is non-internal.
     $properties['non_internal_value'] = DataDefinition::create('string')
-      ->setLabel(new TranslatableMarkup('Computed string, non-internal'))
+      ->setLabel(new TranslatableMarkup('Computed string, non-internal property'))
       ->setComputed(TRUE)
       ->setClass(ComputedString::class)
       ->setInternal(FALSE);
     // Add a computed property that is internal.
     $properties['internal_value'] = DataDefinition::create('string')
-      ->setLabel(new TranslatableMarkup('Computed string, internal'))
+      ->setLabel(new TranslatableMarkup('Computed string, internal property'))
       ->setComputed(TRUE)
       ->setClass(ComputedString::class);
     return $properties;