diff --git a/core/lib/Drupal/Core/Render/Element/Weight.php b/core/lib/Drupal/Core/Render/Element/Weight.php
index 468290a1a7..5b71a1aa24 100644
--- a/core/lib/Drupal/Core/Render/Element/Weight.php
+++ b/core/lib/Drupal/Core/Render/Element/Weight.php
@@ -59,6 +59,10 @@ public static function processWeight(&$element, FormStateInterface $form_state,
       for ($n = (-1 * $element['#delta']); $n <= $element['#delta']; $n++) {
         $weights[$n] = $n;
       }
+      if (!in_array($element['#default_value'], $weights)) {
+        $weights[$element['#default_value']] = $element['#default_value'];
+        ksort($weights);
+      }
       $element['#options'] = $weights;
       $element += $element_info_manager->getInfo('select');
     }
diff --git a/core/tests/Drupal/Tests/Core/Render/Element/WeightTest.php b/core/tests/Drupal/Tests/Core/Render/Element/WeightTest.php
new file mode 100644
index 0000000000..5ca2a70c8d
--- /dev/null
+++ b/core/tests/Drupal/Tests/Core/Render/Element/WeightTest.php
@@ -0,0 +1,52 @@
+<?php
+
+namespace Drupal\Tests\Core\Render\Element;
+
+use Drupal\Core\Form\FormState;
+use Drupal\Core\Render\Element\Weight;
+use Drupal\KernelTests\KernelTestBase;
+
+/**
+ * @coversDefaultClass \Drupal\Core\Render\Element\Weight
+ * @group Render
+ */
+class WeightTest extends KernelTestBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $modules = ['system'];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp() {
+    parent::setUp();
+    $this->installConfig(['system']);
+  }
+
+  /**
+   * Test existing #default_value value in #options list.
+   *
+   * @covers ::processWeight
+   */
+  public function testProcessWeight() {
+    $element = [];
+    $form_state = new FormState();
+    $complete_form = [];
+
+    $element_object = new Weight([], 'weight', []);
+    $info = $element_object->getInfo();
+    $element += $info;
+
+    $element['#default_value'] = $element['#delta'] + 5;
+
+    Weight::processWeight($element, $form_state, $complete_form);
+
+    $this->assertTrue(
+      in_array($element['#default_value'], $element['#options']),
+      'Default value exists in the #options list'
+    );
+  }
+
+}