diff --git a/core/modules/datetime_range/src/Plugin/Field/FieldType/DateRangeItem.php b/core/modules/datetime_range/src/Plugin/Field/FieldType/DateRangeItem.php
index a6755abf2b..f59a3eb66b 100644
--- a/core/modules/datetime_range/src/Plugin/Field/FieldType/DateRangeItem.php
+++ b/core/modules/datetime_range/src/Plugin/Field/FieldType/DateRangeItem.php
@@ -151,4 +151,27 @@ public function onChange($property_name, $notify = TRUE) {
     parent::onChange($property_name, $notify);
   }
 
+  /**
+   * {@inheritdoc}
+   */
+  public function getConstraints() {
+    $constraint_manager = \Drupal::typedDataManager()
+      ->getValidationConstraintManager();
+    $constraints = parent::getConstraints();
+
+    if (empty($this->getSetting('optional_end_date'))) {
+      $label = $this->getFieldDefinition()->getLabel();
+      $constraints[] = $constraint_manager
+        ->create('ComplexData', [
+          'end_value' => [
+            'NotNull' => [
+              'message' => t('The @title end date is required', ['@title' => $label]),
+            ],
+          ],
+        ]);
+    }
+
+    return $constraints;
+  }
+
 }
diff --git a/core/modules/datetime_range/src/Plugin/Field/FieldWidget/DateRangeWidgetBase.php b/core/modules/datetime_range/src/Plugin/Field/FieldWidget/DateRangeWidgetBase.php
index f1f9b2ff4a..772a182462 100644
--- a/core/modules/datetime_range/src/Plugin/Field/FieldWidget/DateRangeWidgetBase.php
+++ b/core/modules/datetime_range/src/Plugin/Field/FieldWidget/DateRangeWidgetBase.php
@@ -131,17 +131,11 @@ public function validateStartEnd(array &$element, FormStateInterface $form_state
     $start_date = $element['value']['#value']['object'];
     $end_date = $element['end_value']['#value']['object'];
 
-    if ($start_date instanceof DrupalDateTime) {
-      if (!$this->getFieldSetting('optional_end_date') && $end_date === NULL) {
-        $form_state->setError($element['end_value'], $this->t('The @title end date is required', ['@title' => $element['#title']]));
-      }
-
-      if ($end_date instanceof DrupalDateTime) {
-        if ($start_date->getTimestamp() !== $end_date->getTimestamp()) {
-          $interval = $start_date->diff($end_date);
-          if ($interval->invert === 1) {
-            $form_state->setError($element, $this->t('The @title end date cannot be before the start date', ['@title' => $element['#title']]));
-          }
+    if ($start_date instanceof DrupalDateTime && $end_date instanceof DrupalDateTime) {
+      if ($start_date->getTimestamp() !== $end_date->getTimestamp()) {
+        $interval = $start_date->diff($end_date);
+        if ($interval->invert === 1) {
+          $form_state->setError($element, $this->t('The @title end date cannot be before the start date', ['@title' => $element['#title']]));
         }
       }
     }
diff --git a/core/modules/datetime_range/tests/src/Kernel/DateRangeItemTest.php b/core/modules/datetime_range/tests/src/Kernel/DateRangeItemTest.php
index 658159a8aa..dd0fe93c6b 100644
--- a/core/modules/datetime_range/tests/src/Kernel/DateRangeItemTest.php
+++ b/core/modules/datetime_range/tests/src/Kernel/DateRangeItemTest.php
@@ -103,4 +103,41 @@ public function testDateOnly() {
     $this->assertEquals('12:00:00', $end_date->format('H:i:s'));
   }
 
+  /**
+   * Test optional end date.
+   */
+  public function testOptionalEndDate() {
+    $field_name = $this->fieldStorage->getName();
+
+    $this->fieldStorage->setSettings([
+        'datetime_type' => DateRangeItem::DATETIME_TYPE_DATE,
+        'optional_end_date' => FALSE,
+      ])
+      ->save();
+
+    $value = [
+      'value' => '2016-09-21',
+      'end_value' => NULL,
+    ];
+
+    // Verify entity without optional_end_date enabled.
+    $entity = EntityTest::create([
+      'name' => $this->randomString(),
+      $field_name => $value,
+    ]);
+    $this->assertNotEqual(count($entity->validate()), 0);
+
+    // Verify entity with the optional_end_date enabled.
+    $this->fieldStorage->setSetting('optional_end_date', TRUE)
+      ->save();
+    $entity = EntityTest::create([
+      'name' => $this->randomString(),
+      $field_name => $value,
+    ]);
+    $this->entityValidateAndSave($entity);
+
+    // Verify changing the date value.
+    $this->assertEqual($entity->{$field_name}->end_value, $value['end_value']);
+  }
+
 }