diff --git a/core/lib/Drupal/Core/Entity/Plugin/Validation/Constraint/EntityChangedConstraint.php b/core/lib/Drupal/Core/Entity/Plugin/Validation/Constraint/EntityChangedConstraint.php
index 6fe462f..d1a21fd 100644
--- a/core/lib/Drupal/Core/Entity/Plugin/Validation/Constraint/EntityChangedConstraint.php
+++ b/core/lib/Drupal/Core/Entity/Plugin/Validation/Constraint/EntityChangedConstraint.php
@@ -9,7 +9,6 @@
 
 use Drupal\Core\Validation\Plugin\Validation\Constraint\ConstraintBase;
 use Drupal\Core\Entity\EntityChangedInterface;
-use Symfony\Component\Validator\Constraint;
 
 /**
  * Validation constraint for the entity changed timestamp.
diff --git a/core/lib/Drupal/Core/Entity/Plugin/Validation/Constraint/EntityTypeConstraint.php b/core/lib/Drupal/Core/Entity/Plugin/Validation/Constraint/EntityTypeConstraint.php
index df25b6c..4e03360 100644
--- a/core/lib/Drupal/Core/Entity/Plugin/Validation/Constraint/EntityTypeConstraint.php
+++ b/core/lib/Drupal/Core/Entity/Plugin/Validation/Constraint/EntityTypeConstraint.php
@@ -7,7 +7,7 @@
 
 namespace Drupal\Core\Entity\Plugin\Validation\Constraint;
 
-use Symfony\Component\Validator\Constraint;
+use Drupal\Core\Validation\Plugin\Validation\Constraint\ConstraintBase;
 
 /**
  * Checks if a value is a valid entity type.
@@ -18,7 +18,7 @@
  *   type = { "entity", "entity_reference" }
  * )
  */
-class EntityTypeConstraint extends Constraint {
+class EntityTypeConstraint extends ConstraintBase {
 
   /**
    * The default violation message.
@@ -47,4 +47,14 @@ public function getDefaultOption() {
   public function getRequiredOptions() {
     return array('type');
   }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function validateValue($entity) {
+    /** @var $entity \Drupal\Core\Entity\EntityInterface */
+    if ($entity->getEntityTypeId() != $this->type) {
+      $this->context->addViolation($this->message, array('%type' => $this->type));
+    }
+  }
 }
diff --git a/core/lib/Drupal/Core/Entity/Plugin/Validation/Constraint/EntityTypeConstraintValidator.php b/core/lib/Drupal/Core/Entity/Plugin/Validation/Constraint/EntityTypeConstraintValidator.php
deleted file mode 100644
index 5e316ca..0000000
--- a/core/lib/Drupal/Core/Entity/Plugin/Validation/Constraint/EntityTypeConstraintValidator.php
+++ /dev/null
@@ -1,29 +0,0 @@
-<?php
-
-/**
- * @file
- * Contains \Drupal\Core\Entity\Plugin\Validation\Constraint\EntityTypeConstraintValidator.
- */
-
-namespace Drupal\Core\Entity\Plugin\Validation\Constraint;
-
-use Drupal\Core\Entity\EntityInterface;
-use Symfony\Component\Validator\Constraint;
-use Symfony\Component\Validator\ConstraintValidator;
-
-/**
- * Validates the EntityType constraint.
- */
-class EntityTypeConstraintValidator extends ConstraintValidator {
-
-  /**
-   * Implements \Symfony\Component\Validator\ConstraintValidatorInterface::validate().
-   */
-  public function validate($entity, Constraint $constraint) {
-
-    /** @var $entity \Drupal\Core\Entity\EntityInterface */
-    if (!empty($entity) && $entity->getEntityTypeId() != $constraint->type) {
-      $this->context->addViolation($constraint->message, array('%type' => $constraint->type));
-    }
-  }
-}
diff --git a/core/lib/Drupal/Core/Entity/Plugin/Validation/Constraint/ValidReferenceConstraint.php b/core/lib/Drupal/Core/Entity/Plugin/Validation/Constraint/ValidReferenceConstraint.php
index 2a7d6a9..c5558a3 100644
--- a/core/lib/Drupal/Core/Entity/Plugin/Validation/Constraint/ValidReferenceConstraint.php
+++ b/core/lib/Drupal/Core/Entity/Plugin/Validation/Constraint/ValidReferenceConstraint.php
@@ -7,7 +7,7 @@
 
 namespace Drupal\Core\Entity\Plugin\Validation\Constraint;
 
-use Symfony\Component\Validator\Constraint;
+use Drupal\Core\Validation\Plugin\Validation\Constraint\ConstraintBase;
 
 /**
  * Entity Reference valid reference constraint.
@@ -19,7 +19,7 @@
  *   label = @Translation("Entity Reference valid reference", context = "Validation")
  * )
  */
-class ValidReferenceConstraint extends Constraint {
+class ValidReferenceConstraint extends ConstraintBase {
 
   /**
    * The default violation message.
@@ -28,4 +28,19 @@ class ValidReferenceConstraint extends Constraint {
    */
   public $message = 'The referenced entity (%type: %id) does not exist.';
 
+  /**
+   * {@inheritdoc}
+   */
+  public function validateValue($value) {
+    $id = $value->get('target_id')->getValue();
+    // '0' or NULL are considered valid empty references.
+    if (empty($id)) {
+      return;
+    }
+    $referenced_entity = $value->get('entity')->getTarget();
+    if (!$referenced_entity) {
+      $type = $value->getFieldDefinition()->getSetting('target_type');
+      $this->context->addViolation($this->message, array('%type' => $type, '%id' => $id));
+    }
+  }
 }
diff --git a/core/lib/Drupal/Core/Entity/Plugin/Validation/Constraint/ValidReferenceConstraintValidator.php b/core/lib/Drupal/Core/Entity/Plugin/Validation/Constraint/ValidReferenceConstraintValidator.php
deleted file mode 100644
index bc269c5..0000000
--- a/core/lib/Drupal/Core/Entity/Plugin/Validation/Constraint/ValidReferenceConstraintValidator.php
+++ /dev/null
@@ -1,36 +0,0 @@
-<?php
-
-/**
- * @file
- * Contains \Drupal\Core\Entity\Plugin\Validation\Constraint\ValidReferenceConstraintValidator.
- */
-
-namespace Drupal\Core\Entity\Plugin\Validation\Constraint;
-
-use Symfony\Component\Validator\Constraint;
-use Symfony\Component\Validator\ConstraintValidator;
-
-/**
- * Checks if referenced entities are valid.
- */
-class ValidReferenceConstraintValidator extends ConstraintValidator {
-
-  /**
-   * {@inheritdoc}
-   */
-  public function validate($value, Constraint $constraint) {
-    if (!isset($value)) {
-      return;
-    }
-    $id = $value->get('target_id')->getValue();
-    // '0' or NULL are considered valid empty references.
-    if (empty($id)) {
-      return;
-    }
-    $referenced_entity = $value->get('entity')->getTarget();
-    if (!$referenced_entity) {
-      $type = $value->getFieldDefinition()->getSetting('target_type');
-      $this->context->addViolation($constraint->message, array('%type' => $type, '%id' => $id));
-    }
-  }
-}