diff --git a/core/lib/Drupal/Core/Entity/EntityManager.php b/core/lib/Drupal/Core/Entity/EntityManager.php
index e9808d2..e40ccc2 100644
--- a/core/lib/Drupal/Core/Entity/EntityManager.php
+++ b/core/lib/Drupal/Core/Entity/EntityManager.php
@@ -599,4 +599,19 @@ public function getAllBundleInfo() {
     return $this->bundleInfo;
   }
 
+  /**
+   * Builds a list of entity type labels suitable for a Form API options list.
+   *
+   * @return array
+   *   An array of entity type labels, keyed by entity type name.
+   */
+  public function getEntityTypeLabels() {
+    $options = array();
+    foreach ($this->getDefinitions() as $entity_type => $definition) {
+      $options[$entity_type] = $definition['label'];
+    }
+
+    return $options;
+  }
+
 }
diff --git a/core/lib/Drupal/Core/Entity/Plugin/DataType/EntityReferenceItem.php b/core/lib/Drupal/Core/Entity/Plugin/DataType/EntityReferenceItem.php
index 5654747..9307f61 100644
--- a/core/lib/Drupal/Core/Entity/Plugin/DataType/EntityReferenceItem.php
+++ b/core/lib/Drupal/Core/Entity/Plugin/DataType/EntityReferenceItem.php
@@ -7,10 +7,10 @@
 
 namespace Drupal\Core\Entity\Plugin\DataType;
 
+use Drupal\Core\Entity\DatabaseStorageController;
 use Drupal\Core\TypedData\Annotation\DataType;
 use Drupal\Core\Annotation\Translation;
 use Drupal\Core\Entity\Field\FieldItemBase;
-use Drupal\Core\TypedData\TypedDataInterface;
 
 /**
  * Defines the 'entity_reference_item' entity field item.
@@ -44,19 +44,35 @@ class EntityReferenceItem extends FieldItemBase {
    * Implements \Drupal\Core\TypedData\ComplexDataInterface::getPropertyDefinitions().
    */
   public function getPropertyDefinitions() {
+    $target_type = $this->definition['settings']['target_type'];
+
     // Definitions vary by entity type and bundle, so key them accordingly.
-    $key = $this->definition['settings']['target_type'] . ':';
+    $key = $target_type . ':';
     $key .= isset($this->definition['settings']['target_bundle']) ? $this->definition['settings']['target_bundle'] : '';
 
     if (!isset(static::$propertyDefinitions[$key])) {
-      static::$propertyDefinitions[$key]['target_id'] = array(
-        // @todo: Lookup the entity type's ID data type and use it here.
-        'type' => 'integer',
-        'label' => t('Entity ID'),
-        'constraints' => array(
-          'Range' => array('min' => 0),
-        ),
-      );
+      $target_type_storage = \Drupal::entityManager()->getStorageController($target_type);
+      if ($target_type_storage instanceof DatabaseStorageController) {
+        static::$propertyDefinitions[$key]['target_id'] = array(
+          'type' => 'integer',
+          'label' => t('Entity ID'),
+          'constraints' => array(
+            'Range' => array('min' => 0),
+          ),
+        );
+      }
+      else {
+        static::$propertyDefinitions[$key]['target_id'] = array(
+          'type' => 'string',
+          'label' => t('Entity ID'),
+          'constraints' => array(
+            'Length' => array(
+              'min' => 0,
+            ),
+          ),
+        );
+      }
+
       static::$propertyDefinitions[$key]['entity'] = array(
         'type' => 'entity_reference',
         'constraints' => array(
diff --git a/core/modules/entity_reference/lib/Drupal/entity_reference/Plugin/entity_reference/selection/SelectionBase.php b/core/modules/entity_reference/lib/Drupal/entity_reference/Plugin/entity_reference/selection/SelectionBase.php
index 74a1a8a..18dc1f4 100644
--- a/core/modules/entity_reference/lib/Drupal/entity_reference/Plugin/entity_reference/selection/SelectionBase.php
+++ b/core/modules/entity_reference/lib/Drupal/entity_reference/Plugin/entity_reference/selection/SelectionBase.php
@@ -10,6 +10,7 @@
 use Drupal\Core\Annotation\Translation;
 use Drupal\Core\Database\Query\AlterableInterface;
 use Drupal\Core\Database\Query\SelectInterface;
+use Drupal\Core\Entity\DatabaseStorageController;
 use Drupal\Core\Entity\EntityInterface;
 use Drupal\Core\Entity\Field\FieldDefinitionInterface;
 use Drupal\Component\Utility\NestedArray;
@@ -102,51 +103,54 @@ public static function settingsForm(FieldDefinitionInterface $field_definition)
       );
     }
 
-    // @todo Use Entity::getPropertyDefinitions() when all entity types are
-    // converted to the new Field API.
-    $fields = drupal_map_assoc(drupal_schema_fields_sql($entity_info['base_table']));
-    foreach (field_info_instances($target_type) as $bundle_instances) {
-      foreach ($bundle_instances as $instance_name => $instance_info) {
-        $field_info = $instance_info->getField();
-        foreach ($field_info['columns'] as $column_name => $column_info) {
-          $fields[$instance_name . '.' . $column_name] = t('@label (@column)', array('@label' => $instance_info['label'], '@column' => $column_name));
+    $target_type_storage = \Drupal::entityManager()->getStorageController($target_type);
+    if ($target_type_storage instanceof DatabaseStorageController) {
+      // @todo Use Entity::getPropertyDefinitions() when all entity types are
+      // converted to the new Field API.
+      $fields = drupal_map_assoc(drupal_schema_fields_sql($entity_info['base_table']));
+      foreach (field_info_instances($target_type) as $bundle_instances) {
+        foreach ($bundle_instances as $instance_name => $instance_info) {
+          $field_info = $instance_info->getField();
+          foreach ($field_info['columns'] as $column_name => $column_info) {
+            $fields[$instance_name . '.' . $column_name] = t('@label (@column)', array('@label' => $instance_info['label'], '@column' => $column_name));
+          }
         }
       }
-    }
-
-    $form['sort']['field'] = array(
-      '#type' => 'select',
-      '#title' => t('Sort by'),
-      '#options' => array(
-        '_none' => t('- None -'),
-      ) + $fields,
-      '#ajax' => TRUE,
-      '#limit_validation_errors' => array(),
-      '#default_value' => $selection_handler_settings['sort']['field'],
-    );
-
-    $form['sort']['settings'] = array(
-      '#type' => 'container',
-      '#attributes' => array('class' => array('entity_reference-settings')),
-      '#process' => array('_entity_reference_form_process_merge_parent'),
-    );
-
-    if ($selection_handler_settings['sort']['field'] != '_none') {
-      // Merge-in default values.
-      $selection_handler_settings['sort'] += array(
-        'direction' => 'ASC',
-      );
 
-      $form['sort']['settings']['direction'] = array(
+      $form['sort']['field'] = array(
         '#type' => 'select',
-        '#title' => t('Sort direction'),
-        '#required' => TRUE,
+        '#title' => t('Sort by'),
         '#options' => array(
-          'ASC' => t('Ascending'),
-          'DESC' => t('Descending'),
-        ),
-        '#default_value' => $selection_handler_settings['sort']['direction'],
+          '_none' => t('- None -'),
+        ) + $fields,
+        '#ajax' => TRUE,
+        '#limit_validation_errors' => array(),
+        '#default_value' => $selection_handler_settings['sort']['field'],
+      );
+
+      $form['sort']['settings'] = array(
+        '#type' => 'container',
+        '#attributes' => array('class' => array('entity_reference-settings')),
+        '#process' => array('_entity_reference_form_process_merge_parent'),
       );
+
+      if ($selection_handler_settings['sort']['field'] != '_none') {
+        // Merge-in default values.
+        $selection_handler_settings['sort'] += array(
+          'direction' => 'ASC',
+        );
+
+        $form['sort']['settings']['direction'] = array(
+          '#type' => 'select',
+          '#title' => t('Sort direction'),
+          '#required' => TRUE,
+          '#options' => array(
+            'ASC' => t('Ascending'),
+            'DESC' => t('Descending'),
+          ),
+          '#default_value' => $selection_handler_settings['sort']['direction'],
+        );
+      }
     }
 
     return $form;
diff --git a/core/modules/entity_reference/lib/Drupal/entity_reference/Plugin/field/field_type/ConfigurableEntityReferenceItem.php b/core/modules/entity_reference/lib/Drupal/entity_reference/Plugin/field/field_type/ConfigurableEntityReferenceItem.php
index ee5e79a..f221570 100644
--- a/core/modules/entity_reference/lib/Drupal/entity_reference/Plugin/field/field_type/ConfigurableEntityReferenceItem.php
+++ b/core/modules/entity_reference/lib/Drupal/entity_reference/Plugin/field/field_type/ConfigurableEntityReferenceItem.php
@@ -7,13 +7,10 @@
 
 namespace Drupal\entity_reference\Plugin\field\field_type;
 
-use Drupal\Core\Annotation\Translation;
-use Drupal\Core\Entity\Annotation\FieldType;
-use Drupal\Core\Entity\Field\Type\EntityReferenceItem;
+use Drupal\Core\Entity\DatabaseStorageController;
+use Drupal\field\FieldInterface;
 use Drupal\field\Plugin\Type\FieldType\ConfigEntityReferenceItemBase;
-use Drupal\field\Plugin\Type\FieldType\ConfigFieldItemBase;
 use Drupal\field\Plugin\Type\FieldType\ConfigFieldItemInterface;
-use Drupal\field\FieldInterface;
 
 /**
  * Plugin implementation of the 'entity_reference' field type.
@@ -46,8 +43,11 @@ class ConfigurableEntityReferenceItem extends ConfigEntityReferenceItemBase impl
    * {@inheritdoc}
    */
   public static function schema(FieldInterface $field) {
-    $schema = array(
-      'columns' => array(
+    $target_type = $field->getFieldSetting('target_type');
+    $target_type_storage = \Drupal::entityManager()->getStorageController($target_type);
+
+    if ($target_type_storage instanceof DatabaseStorageController) {
+      $columns = array(
         'target_id' => array(
           'description' => 'The ID of the target entity.',
           'type' => 'int',
@@ -60,26 +60,25 @@ public static function schema(FieldInterface $field) {
           'unsigned' => TRUE,
           'not null' => FALSE,
         ),
-      ),
+      );
+    }
+    else {
+      $columns = array(
+        'target_id' => array(
+          'description' => 'The ID of the target entity.',
+          'type' => 'varchar',
+          'length' => '255',
+        ),
+      );
+    }
+
+    $schema = array(
+      'columns' => $columns,
       'indexes' => array(
         'target_id' => array('target_id'),
       ),
     );
 
-    // Create a foreign key to the target entity type base type.
-    $entity_manager = \Drupal::service('entity.manager');
-    if (is_subclass_of($entity_manager->getControllerClass($field['settings']['target_type'], 'storage'), 'Drupal\Core\Entity\DatabaseStorageController')) {
-      $entity_info = $entity_manager->getDefinition($field['settings']['target_type']);
-
-      $base_table = $entity_info['base_table'];
-      $id_column = $entity_info['entity_keys']['id'];
-
-      $schema['foreign keys'][$base_table] = array(
-        'table' => $base_table,
-        'columns' => array('target_id' => $id_column),
-      );
-    }
-
     return $schema;
   }
 
@@ -100,21 +99,10 @@ public function preSave() {
    * {@inheritdoc}
    */
   public function settingsForm(array $form, array &$form_state, $has_data) {
-    // Select the target entity type.
-    $entity_type_options = array();
-    foreach (\Drupal::entityManager()->getDefinitions() as $entity_type => $entity_info) {
-      // @todo As the database schema can currently only store numeric IDs of
-      // referenced entities and configuration entities have string IDs, prevent
-      // configuration entities from being referenced.
-      if (!is_subclass_of($entity_info['class'], '\Drupal\Core\Config\Entity\ConfigEntityInterface')) {
-        $entity_type_options[$entity_type] = $entity_info['label'];
-      }
-    }
-
     $element['target_type'] = array(
       '#type' => 'select',
       '#title' => t('Type of item to reference'),
-      '#options' => $entity_type_options,
+      '#options' => \Drupal::entityManager()->getEntityTypeLabels(),
       '#default_value' => $this->getFieldSetting('target_type'),
       '#required' => TRUE,
       '#disabled' => $has_data,
diff --git a/core/modules/entity_reference/lib/Drupal/entity_reference/Tests/EntityReferenceAdminTest.php b/core/modules/entity_reference/lib/Drupal/entity_reference/Tests/EntityReferenceAdminTest.php
index acef71e..1ef3608 100644
--- a/core/modules/entity_reference/lib/Drupal/entity_reference/Tests/EntityReferenceAdminTest.php
+++ b/core/modules/entity_reference/lib/Drupal/entity_reference/Tests/EntityReferenceAdminTest.php
@@ -75,6 +75,11 @@ public function testFieldAdminHandler() {
     // Node should be selected by default.
     $this->assertFieldByName('field[settings][target_type]', 'node');
 
+    // Check that all entity types can be referenced.
+    foreach (\Drupal::entityManager()->getDefinitions() as $entity_type => $entity_info) {
+      $this->assertFieldByXPath("//select[@name='field[settings][target_type]']/option[@value='" . $entity_type . "']");
+    }
+
     // Second step: 'Instance settings' form.
     $this->drupalPostForm(NULL, array(), t('Save field settings'));
 
diff --git a/core/modules/entity_reference/lib/Drupal/entity_reference/Tests/EntityReferenceItemTest.php b/core/modules/entity_reference/lib/Drupal/entity_reference/Tests/EntityReferenceItemTest.php
index b37030a..b01e024 100644
--- a/core/modules/entity_reference/lib/Drupal/entity_reference/Tests/EntityReferenceItemTest.php
+++ b/core/modules/entity_reference/lib/Drupal/entity_reference/Tests/EntityReferenceItemTest.php
@@ -8,6 +8,7 @@
 namespace Drupal\entity_reference\Tests;
 
 use Drupal\Core\Entity\DatabaseStorageController;
+use Drupal\Core\Entity\EntityInterface;
 use Drupal\Core\Entity\Field\FieldItemListInterface;
 use Drupal\Core\Entity\Field\FieldItemInterface;
 use Drupal\Core\Language\Language;
@@ -25,6 +26,20 @@ class EntityReferenceItemTest extends FieldUnitTestBase {
    */
   public static $modules = array('entity_reference', 'taxonomy', 'options');
 
+  /**
+   * The taxonomy vocabulary to test with.
+   *
+   * @var \Drupal\taxonomy\VocabularyInterface
+   */
+  protected $vocabulary;
+
+  /**
+   * The taxonomy term to test with.
+   *
+   * @var \Drupal\taxonomy\TermInterface
+   */
+  protected $term;
+
   public static function getInfo() {
     return array(
       'name' => 'Entity Reference field item',
@@ -42,48 +57,49 @@ public function setUp() {
     $this->installSchema('taxonomy', 'taxonomy_term_data');
     $this->installSchema('taxonomy', 'taxonomy_term_hierarchy');
 
-    $vocabulary = entity_create('taxonomy_vocabulary', array(
+    $this->vocabulary = entity_create('taxonomy_vocabulary', array(
       'name' => $this->randomName(),
       'vid' => drupal_strtolower($this->randomName()),
       'langcode' => Language::LANGCODE_NOT_SPECIFIED,
     ));
-    $vocabulary->save();
+    $this->vocabulary->save();
 
     $this->term = entity_create('taxonomy_term', array(
       'name' => $this->randomName(),
-      'vid' => $vocabulary->id(),
+      'vid' => $this->vocabulary->id(),
       'langcode' => Language::LANGCODE_NOT_SPECIFIED,
     ));
     $this->term->save();
 
     // Use the util to create an instance.
-    entity_reference_create_instance('entity_test', 'entity_test', 'field_test_taxonomy', 'Test entity reference', 'taxonomy_term');
+    entity_reference_create_instance('entity_test', 'entity_test', 'field_test_taxonomy_term', 'Test content entity reference', 'taxonomy_term');
+    entity_reference_create_instance('entity_test', 'entity_test', 'field_test_taxonomy_vocabulary', 'Test config entity reference', 'taxonomy_vocabulary');
   }
 
   /**
-   * Tests using entity fields of the entity reference field type.
+   * Tests the entity reference field type for referencing content entities.
    */
-  public function testEntityReferenceItem() {
+  public function testContentEntityReferenceItem() {
     $tid = $this->term->id();
 
     // Just being able to create the entity like this verifies a lot of code.
     $entity = entity_create('entity_test', array());
-    $entity->field_test_taxonomy->target_id = $tid;
+    $entity->field_test_taxonomy_term->target_id = $tid;
     $entity->name->value = $this->randomName();
     $entity->save();
 
     $entity = entity_load('entity_test', $entity->id());
-    $this->assertTrue($entity->field_test_taxonomy instanceof FieldItemListInterface, 'Field implements interface.');
-    $this->assertTrue($entity->field_test_taxonomy[0] instanceof FieldItemInterface, 'Field item implements interface.');
-    $this->assertEqual($entity->field_test_taxonomy->target_id, $tid);
-    $this->assertEqual($entity->field_test_taxonomy->entity->name->value, $this->term->name->value);
-    $this->assertEqual($entity->field_test_taxonomy->entity->id(), $tid);
-    $this->assertEqual($entity->field_test_taxonomy->entity->uuid(), $this->term->uuid());
+    $this->assertTrue($entity->field_test_taxonomy_term instanceof FieldItemListInterface, 'Field implements interface.');
+    $this->assertTrue($entity->field_test_taxonomy_term[0] instanceof FieldItemInterface, 'Field item implements interface.');
+    $this->assertEqual($entity->field_test_taxonomy_term->target_id, $tid);
+    $this->assertEqual($entity->field_test_taxonomy_term->entity->name->value, $this->term->name->value);
+    $this->assertEqual($entity->field_test_taxonomy_term->entity->id(), $tid);
+    $this->assertEqual($entity->field_test_taxonomy_term->entity->uuid(), $this->term->uuid());
 
     // Change the name of the term via the reference.
     $new_name = $this->randomName();
-    $entity->field_test_taxonomy->entity->name = $new_name;
-    $entity->field_test_taxonomy->entity->save();
+    $entity->field_test_taxonomy_term->entity->name = $new_name;
+    $entity->field_test_taxonomy_term->entity->save();
     // Verify it is the correct name.
     $term = entity_load('taxonomy_term', $tid);
     $this->assertEqual($term->name->value, $new_name);
@@ -96,9 +112,9 @@ public function testEntityReferenceItem() {
     ));
     $term2->save();
 
-    $entity->field_test_taxonomy->target_id = $term2->id();
-    $this->assertEqual($entity->field_test_taxonomy->entity->id(), $term2->id());
-    $this->assertEqual($entity->field_test_taxonomy->entity->name->value, $term2->name->value);
+    $entity->field_test_taxonomy_term->target_id = $term2->id();
+    $this->assertEqual($entity->field_test_taxonomy_term->entity->id(), $term2->id());
+    $this->assertEqual($entity->field_test_taxonomy_term->entity->name->value, $term2->name->value);
 
     // Delete terms so we have nothing to reference and try again
     $term->delete();
@@ -108,30 +124,50 @@ public function testEntityReferenceItem() {
   }
 
   /**
-   * Tests foreign key support.
+   * Tests the entity reference field type for referencing config entities.
    */
-  public function testEntityReferenceFieldSchema() {
-    $field = field_info_field('entity_test', 'field_test_taxonomy');
-    $foreign_key_column_name = 'target_id';
-
-    // Grab the SQL schema and verify that the 'foreign keys' are present.
-    $schemas = DatabaseStorageController::_fieldSqlSchema($field);
-    $schema = $schemas[DatabaseStorageController::_fieldTableName($field)];
-    $this->assertEqual(count($schema['foreign keys']), 1, 'There is 1 foreign key in the schema.');
-
-    $foreign_key = reset($schema['foreign keys']);
-    $foreign_key_column = DatabaseStorageController::_fieldColumnName($field, $foreign_key_column_name);
-    $this->assertEqual($foreign_key['table'], 'taxonomy_term_data', 'Foreign key table name preserved in the schema.');
-    $this->assertEqual($foreign_key['columns'][$foreign_key_column], 'tid', 'Foreign key column name preserved in the schema.');
-
-    // Create a field that references a config entity type and check that no
-    // foreign key is present.
-    $field_name = 'field_test_vocabulary';
-    entity_reference_create_instance('entity_test', 'entity_test', $field_name, 'Test vocabulary reference', 'taxonomy_vocabulary');
-    $field = field_info_field('entity_test', $field_name);
-
-    $schemas = DatabaseStorageController::_fieldSqlSchema($field);
-    $schema = $schemas[DatabaseStorageController::_fieldTableName($field)];
-    $this->assertFalse(isset($schema['foreign keys']), 'There is no foreign key in the schema.');
+  public function testConfigEntityReferenceItem() {
+    $referenced_entity_id = $this->vocabulary->id();
+
+    // Just being able to create the entity like this verifies a lot of code.
+    $entity = entity_create('entity_test', array());
+    $entity->field_test_taxonomy_vocabulary->target_id = $referenced_entity_id;
+    $entity->name->value = $this->randomName();
+    $entity->save();
+
+    $entity = entity_load('entity_test', $entity->id());
+    $this->assertTrue($entity->field_test_taxonomy_vocabulary instanceof FieldItemListInterface, 'Field implements interface.');
+    $this->assertTrue($entity->field_test_taxonomy_vocabulary[0] instanceof FieldItemInterface, 'Field item implements interface.');
+    $this->assertEqual($entity->field_test_taxonomy_vocabulary->target_id, $referenced_entity_id);
+    $this->assertEqual($entity->field_test_taxonomy_vocabulary->entity->name, $this->vocabulary->name);
+    $this->assertEqual($entity->field_test_taxonomy_vocabulary->entity->id(), $referenced_entity_id);
+    $this->assertEqual($entity->field_test_taxonomy_vocabulary->entity->uuid(), $this->vocabulary->uuid());
+
+    // Change the name of the term via the reference.
+    $new_name = $this->randomName();
+    $entity->field_test_taxonomy_vocabulary->entity->name = $new_name;
+    $entity->field_test_taxonomy_vocabulary->entity->save();
+    // Verify it is the correct name.
+    $term = entity_load('taxonomy_vocabulary', $referenced_entity_id);
+    $this->assertEqual($term->name, $new_name);
+
+    // Make sure the computed term reflects updates to the term id.
+    $vocabulary2 = entity_create('taxonomy_vocabulary', array(
+      'name' => $this->randomName(),
+      'vid' => drupal_strtolower($this->randomName()),
+      'langcode' => Language::LANGCODE_NOT_SPECIFIED,
+    ));
+    $vocabulary2->save();
+
+    $entity->field_test_taxonomy_vocabulary->target_id = $vocabulary2->id();
+    $this->assertEqual($entity->field_test_taxonomy_vocabulary->entity->id(), $vocabulary2->id());
+    $this->assertEqual($entity->field_test_taxonomy_vocabulary->entity->name, $vocabulary2->name);
+
+    // Delete terms so we have nothing to reference and try again
+    $this->vocabulary->delete();
+    $vocabulary2->delete();
+    $entity = entity_create('entity_test', array('name' => $this->randomName()));
+    $entity->save();
   }
+
 }
diff --git a/core/modules/field/lib/Drupal/field/Plugin/Type/FieldType/ConfigEntityReferenceItemBase.php b/core/modules/field/lib/Drupal/field/Plugin/Type/FieldType/ConfigEntityReferenceItemBase.php
index 6b3c137..7d0aae1 100644
--- a/core/modules/field/lib/Drupal/field/Plugin/Type/FieldType/ConfigEntityReferenceItemBase.php
+++ b/core/modules/field/lib/Drupal/field/Plugin/Type/FieldType/ConfigEntityReferenceItemBase.php
@@ -7,10 +7,11 @@
 
 namespace Drupal\field\Plugin\Type\FieldType;
 
+use Drupal\Core\Entity\DatabaseStorageController;
 use Drupal\Core\Entity\Plugin\DataType\EntityReferenceItem;
-use Drupal\field\Plugin\Type\FieldType\ConfigFieldItemInterface;
-use Drupal\field\FieldInterface;
 use Drupal\field\FieldInstanceInterface;
+use Drupal\field\FieldInterface;
+use Drupal\field\Plugin\Type\FieldType\ConfigFieldItemInterface;
 
 /**
  * A common base class for configurable entity reference fields.
@@ -36,22 +37,28 @@ class ConfigEntityReferenceItemBase extends EntityReferenceItem implements Confi
    * {@inheritdoc}
    */
   public function getPropertyDefinitions() {
+    $target_type = $this->definition['settings']['target_type'];
+
     // Definitions vary by entity type and bundle, so key them accordingly.
-    $key = $this->definition['settings']['target_type'] . ':';
+    $key = $target_type . ':';
     $key .= isset($this->definition['settings']['target_bundle']) ? $this->definition['settings']['target_bundle'] : '';
 
     if (!isset(static::$propertyDefinitions[$key])) {
       // Call the parent to define the target_id and entity properties.
       parent::getPropertyDefinitions();
 
-      static::$propertyDefinitions[$key]['revision_id'] = array(
-        // @todo: Lookup the entity type's ID data type and use it here.
-        'type' => 'integer',
-        'label' => t('Revision ID'),
-        'constraints' => array(
-          'Range' => array('min' => 0),
-        ),
-      );
+      // Only add the revision ID property if content entity target types.
+      $target_type_storage = \Drupal::entityManager()->getStorageController($target_type);
+      if ($target_type_storage instanceof DatabaseStorageController) {
+        static::$propertyDefinitions[$key]['revision_id'] = array(
+          'type' => 'integer',
+          'label' => t('Revision ID'),
+          'constraints' => array(
+            'Range' => array('min' => 0),
+          ),
+        );
+      }
+
       static::$propertyDefinitions[$key]['label'] = array(
         'type' => 'string',
         'label' => t('Label (auto-create)'),
@@ -88,7 +95,7 @@ public static function schema(FieldInterface $field) {
   public function isEmpty() {
     // Avoid loading the entity by first checking the 'target_id'.
     $target_id = $this->get('target_id')->getValue();
-    if (!empty($target_id) && is_numeric($target_id)) {
+    if (!empty($target_id) && (is_numeric($target_id) || is_string($target_id))) {
       return FALSE;
     }
     // Allow auto-create entities.
diff --git a/core/modules/system/lib/Drupal/system/Tests/TypedData/TypedDataTest.php b/core/modules/system/lib/Drupal/system/Tests/TypedData/TypedDataTest.php
index d0d61fa..ad8efe0 100644
--- a/core/modules/system/lib/Drupal/system/Tests/TypedData/TypedDataTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/TypedData/TypedDataTest.php
@@ -28,7 +28,7 @@ class TypedDataTest extends DrupalUnitTestBase {
    *
    * @var array
    */
-  public static $modules = array('system', 'entity', 'field', 'file');
+  public static $modules = array('system', 'entity', 'field', 'file', 'user');
 
   public static function getInfo() {
     return array(
diff --git a/core/modules/text/lib/Drupal/text/Tests/Formatter/TextPlainUnitTest.php b/core/modules/text/lib/Drupal/text/Tests/Formatter/TextPlainUnitTest.php
index 1ef1d3b..72c0fe9 100644
--- a/core/modules/text/lib/Drupal/text/Tests/Formatter/TextPlainUnitTest.php
+++ b/core/modules/text/lib/Drupal/text/Tests/Formatter/TextPlainUnitTest.php
@@ -26,7 +26,7 @@ class TextPlainUnitTest extends DrupalUnitTestBase {
    *
    * @var array
    */
-  public static $modules = array('entity', 'field', 'text', 'entity_test', 'system', 'filter');
+  public static $modules = array('entity', 'field', 'text', 'entity_test', 'system', 'filter', 'user');
 
   /**
    * Contains rendered content.
diff --git a/core/modules/views/lib/Drupal/views/Tests/QueryGroupByTest.php b/core/modules/views/lib/Drupal/views/Tests/QueryGroupByTest.php
index edb6737..e442cb4 100644
--- a/core/modules/views/lib/Drupal/views/Tests/QueryGroupByTest.php
+++ b/core/modules/views/lib/Drupal/views/Tests/QueryGroupByTest.php
@@ -24,7 +24,7 @@ class QueryGroupByTest extends ViewUnitTestBase {
    *
    * @var array
    */
-  public static $modules = array('entity_test', 'system', 'field');
+  public static $modules = array('entity_test', 'system', 'field', 'user');
 
   /**
    * The storage controller for the test entity type.