diff -u b/core/lib/Drupal/Core/Entity/Plugin/DataType/Deriver/EntityDeriver.php b/core/lib/Drupal/Core/Entity/Plugin/DataType/Deriver/EntityDeriver.php
--- b/core/lib/Drupal/Core/Entity/Plugin/DataType/Deriver/EntityDeriver.php
+++ b/core/lib/Drupal/Core/Entity/Plugin/DataType/Deriver/EntityDeriver.php
@@ -89,7 +89,7 @@
       $this->derivatives[$entity_type_id] = [
         'label' => $entity_type->getLabel(),
         'constraints' => $entity_type->getConstraints(),
-        'internal' => $entity_type->getKey('internal'),
+        'internal' => $entity_type->get('internal'),
       ] + $base_plugin_definition;
 
       // Incorporate the bundles as entity:$entity_type:$bundle, if any.
reverted:
--- b/core/lib/Drupal/Core/Entity/Plugin/DataType/EntityAdapter.php
+++ a/core/lib/Drupal/Core/Entity/Plugin/DataType/EntityAdapter.php
@@ -44,12 +44,9 @@
    * @return static
    */
   public static function createFromEntity(EntityInterface $entity) {
+    $definition = EntityDataDefinition::create()
+      ->setEntityTypeId($entity->getEntityTypeId())
+      ->setBundles([$entity->bundle()]);
-    $entity_type_id = $entity->getEntityTypeId();
-    $bundle = $entity->bundle();
-    $definition = EntityDataDefinition::create(
-      $entity_type_id,
-      ($bundle !== $entity_type_id) ? $bundle : NULL
-    );
     $instance = new static($definition);
     $instance->setValue($entity);
     return $instance;
diff -u b/core/tests/Drupal/KernelTests/Core/Entity/EntityTypedDataDefinitionTest.php b/core/tests/Drupal/KernelTests/Core/Entity/EntityTypedDataDefinitionTest.php
--- b/core/tests/Drupal/KernelTests/Core/Entity/EntityTypedDataDefinitionTest.php
+++ b/core/tests/Drupal/KernelTests/Core/Entity/EntityTypedDataDefinitionTest.php
@@ -151,7 +151,7 @@
     $entity_type = $this->prophesize(EntityTypeInterface::class);
     $entity_type->getLabel()->willReturn($this->randomString());
     $entity_type->getConstraints()->willReturn([]);
-    $entity_type->getKey('internal')->willReturn($internal);
+    $entity_type->get('internal')->willReturn($internal);
 
     $entity_manager = $this->prophesize(EntityManagerInterface::class);
     $entity_manager->getDefinitions()->willReturn([$entity_type_id => $entity_type->reveal()]);
reverted:
--- b/core/tests/Drupal/Tests/Core/Entity/TypedData/EntityAdapterUnitTest.php
+++ a/core/tests/Drupal/Tests/Core/Entity/TypedData/EntityAdapterUnitTest.php
@@ -159,7 +159,7 @@
     $this->typedDataManager = $this->getMock(TypedDataManagerInterface::class);
     $this->typedDataManager->expects($this->any())
       ->method('getDefinition')
+      ->with('entity')
-      ->with("entity:{$this->entityTypeId}:{$this->bundle}")
       ->will($this->returnValue(['class' => '\Drupal\Core\Entity\Plugin\DataType\EntityAdapter']));
     $this->typedDataManager->expects($this->any())
       ->method('getDefaultConstraints')