diff -u b/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/EntityReferenceItem.php b/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/EntityReferenceItem.php
--- b/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/EntityReferenceItem.php
+++ b/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/EntityReferenceItem.php
@@ -22,9 +22,6 @@
  *
  * Supported settings (below the definition's 'settings' key) are:
  * - target_type: The entity type to reference. Required.
- * - target_bundle: (optional): If set, restricts the entity bundles which may
- *   may be referenced. May be set to an single bundle, or to an array of
- *   allowed bundles.
  *
  * @FieldType(
  *   id = "entity_reference",
only in patch2:
unchanged:
--- a/core/modules/entity_reference/src/ConfigurableEntityReferenceItem.php
+++ b/core/modules/entity_reference/src/ConfigurableEntityReferenceItem.php
@@ -33,17 +33,6 @@ class ConfigurableEntityReferenceItem extends EntityReferenceItem implements Opt
   /**
    * {@inheritdoc}
    */
-  public static function defaultStorageSettings() {
-    $settings = parent::defaultStorageSettings();
-    // The target bundle is handled by the 'target_bundles' property in the
-    // 'handler_settings' instance setting.
-    unset($settings['target_bundle']);
-    return $settings;
-  }
-
-  /**
-   * {@inheritdoc}
-   */
   public function getPossibleValues(AccountInterface $account = NULL) {
     return $this->getSettableValues($account);
   }
only in patch2:
unchanged:
--- a/core/modules/field/src/Tests/Migrate/d6/MigrateFieldInstanceTest.php
+++ b/core/modules/field/src/Tests/Migrate/d6/MigrateFieldInstanceTest.php
@@ -126,7 +126,6 @@ public function testFieldInstanceSettings() {
       // storages so we end up with the default value for this setting.
       'handler' => 'default:node',
       'handler_settings' => array(),
-      'target_bundle' => NULL,
     );
     $field_settings = $field->getSettings();
     ksort($expected);
only in patch2:
unchanged:
--- a/core/modules/system/src/Tests/Entity/EntityFieldTest.php
+++ b/core/modules/system/src/Tests/Entity/EntityFieldTest.php
@@ -689,7 +689,7 @@ public function testEntityConstraintValidation() {
     $definition = BaseFieldDefinition::create('entity_reference')
       ->setLabel('Test entity')
       ->setSetting('target_type', 'node')
-      ->setSetting('target_bundle', 'article');
+      ->setSetting('handler_settings', ['target_bundles' => ['article' => 'article']]);
     $reference_field = \Drupal::TypedDataManager()->create($definition);
     $reference = $reference_field->appendItem(array('entity' => $node))->get('entity');
     $violations = $reference->validate();
only in patch2:
unchanged:
--- a/core/modules/system/system.install
+++ b/core/modules/system/system.install
@@ -1643,5 +1643,30 @@ function system_update_8007() {
 }
 
 /**
++ * Removes the stale 'target_bundle' setting for entity_reference fields.
++ */
+function system_update_8008() {
+  $config = \Drupal::configFactory();
+  /** @var \Drupal\Core\Field\FieldTypePluginManager $field_type_manager */
+  $field_type_manager = \Drupal::service('plugin.manager.field.field_type');
+  $item_class = 'Drupal\Core\Field\Plugin\Field\FieldType\EntityReferenceItem';
+
+  // Iterate on all fields storage.
+  foreach ($config->listAll('field.storage.') as $field_id) {
+    $field_storage = $config->getEditable($field_id);
+    $class = $field_type_manager->getPluginClass($field_storage->get('type'));
+
+    // Deal only with entity reference fields and descendants.
+    if ($class != $item_class && !is_subclass_of($class, $item_class)) {
+      continue;
+    }
+
+    // Remove 'target_bundle' from settings.
+    $field_storage->clear('settings.target_bundle');
+    $field_storage->save(TRUE);
+  }
+}
+
+/**
  * @} End of "addtogroup updates-8.0.0-beta".
  */