diff --git a/core/config/schema/core.data_types.schema.yml b/core/config/schema/core.data_types.schema.yml
index ef68a3e..1094a53 100644
--- a/core/config/schema/core.data_types.schema.yml
+++ b/core/config/schema/core.data_types.schema.yml
@@ -556,8 +556,11 @@ field.entity_reference.value:
       label: 'Default'
       mapping:
         target_id:
-          type: integer
+          type: string
           label: 'Value'
+        target_uuid:
+          type: string
+          label: 'Target UUID'
 
 # Schema for the configuration of the Boolean field type.
 
diff --git a/core/modules/entity_reference/src/Tests/EntityReferenceFieldDefaultValueTest.php b/core/modules/entity_reference/src/Tests/EntityReferenceFieldDefaultValueTest.php
index 497d39e..aacc4b5 100644
--- a/core/modules/entity_reference/src/Tests/EntityReferenceFieldDefaultValueTest.php
+++ b/core/modules/entity_reference/src/Tests/EntityReferenceFieldDefaultValueTest.php
@@ -8,6 +8,7 @@
 namespace Drupal\entity_reference\Tests;
 
 use Drupal\Component\Utility\Unicode;
+use Drupal\config\Tests\SchemaCheckTestTrait;
 use Drupal\simpletest\WebTestBase;
 
 /**
@@ -16,6 +17,7 @@
  * @group entity_reference
  */
 class EntityReferenceFieldDefaultValueTest extends WebTestBase {
+  use SchemaCheckTestTrait;
 
   /**
    * Modules to install.
@@ -88,6 +90,12 @@ function testEntityReferenceDefaultValue() {
     // Create a new node to check that UUID has been converted to numeric ID.
     $new_node = entity_create('node', array('type' => 'reference_content'));
     $this->assertEqual($new_node->get($field_name)->offsetGet(0)->target_id, $referenced_node->id());
+
+    // Ensure that the entity reference config schemas are correct.
+    $field_config = \Drupal::config('field.field.node.reference_content.' . $field_name);
+    $this->assertConfigSchema(\Drupal::service('config.typed'), $field_config->getName(), $field_config->get());
+    $field_storage_config = \Drupal::config('field.storage.node.' . $field_name);
+    $this->assertConfigSchema(\Drupal::service('config.typed'), $field_storage_config->getName(), $field_storage_config->get());
   }
 
 }
diff --git a/core/modules/entity_reference/src/Tests/EntityReferenceFieldTest.php b/core/modules/entity_reference/src/Tests/EntityReferenceFieldTest.php
index 74d3b31..115998e 100644
--- a/core/modules/entity_reference/src/Tests/EntityReferenceFieldTest.php
+++ b/core/modules/entity_reference/src/Tests/EntityReferenceFieldTest.php
@@ -7,6 +7,8 @@
 
 namespace Drupal\entity_reference\Tests;
 
+use Drupal\config\Tests\SchemaCheckTestTrait;
+use Drupal\field\Entity\FieldConfig;
 use Drupal\system\Tests\Entity\EntityUnitTestBase;
 use Drupal\Core\Field\FieldStorageDefinitionInterface;
 
@@ -16,6 +18,7 @@
  * @group entity_reference
  */
 class EntityReferenceFieldTest extends EntityUnitTestBase {
+  use SchemaCheckTestTrait;
 
   /**
    * The entity type used in this test.
@@ -147,4 +150,47 @@ public function testReferencedEntitiesMultipleLoad() {
     }
   }
 
+  /**
+   * Tests referencing entities with string IDs.
+   */
+  public function testReferencedEntitiesStringId() {
+    $field_name = 'entity_reference_string_id';
+    $this->installEntitySchema('entity_test_string_id');
+    entity_reference_create_field(
+      $this->entityType,
+      $this->bundle,
+      $field_name,
+      'Field test',
+      'entity_test_string_id',
+      'default',
+      array('target_bundles' => array($this->bundle)),
+      FieldStorageDefinitionInterface::CARDINALITY_UNLIMITED
+    );
+    // Create the parent entity.
+    $entity = entity_create($this->entityType, array('type' => $this->bundle));
+
+    // Create the default target entity.
+    $target_entity = entity_create('entity_test_string_id', array('id' => $this->randomString(), 'type' => $this->bundle));
+    $target_entity->save();
+
+    // Set the field value.
+    $entity->{$field_name}->setValue(array(array('target_id' => $target_entity->id())));
+
+    // Load the target entities using EntityReferenceField::referencedEntities().
+    $entities = $entity->{$field_name}->referencedEntities();
+    $this->assertEqual($entities[0]->id(), $target_entity->id());
+
+    // Test that a string ID works as a default value and the field's config
+    // schema is correct.
+    $field = FieldConfig::loadByName($this->entityType, $this->bundle, $field_name);
+    $field->setDefaultValue($target_entity->id());
+    $field->save();
+    $this->assertConfigSchema(\Drupal::service('config.typed'), 'field.field.' . $field->id(), $field->toArray());
+
+    // Test that the default value works.
+    $entity = entity_create($this->entityType, array('type' => $this->bundle));
+    $entities = $entity->{$field_name}->referencedEntities();
+    $this->assertEqual($entities[0]->id(), $target_entity->id());
+  }
+
 }