diff --git a/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/UriItem.php b/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/UriItem.php
index 1481d88..9d62405 100644
--- a/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/UriItem.php
+++ b/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/UriItem.php
@@ -7,6 +7,8 @@
 
 namespace Drupal\Core\Field\Plugin\Field\FieldType;
 
+use Drupal\Component\Utility\Unicode;
+use Drupal\Core\Field\FieldDefinitionInterface;
 use Drupal\Core\Field\FieldStorageDefinitionInterface;
 use Drupal\Core\TypedData\DataDefinition;
 
@@ -77,4 +79,16 @@ public function isEmpty() {
     return parent::isEmpty();
   }
 
+  /**
+   * {@inheritdoc}
+   */
+  public static function generateSampleValue(FieldDefinitionInterface $field_definition) {
+    $values = parent::generateSampleValue($field_definition);
+    $suffix_length = $field_definition->getSetting('max_length') - 7;
+    foreach ($values as $key => $value) {
+      $values[$key] = 'http://' . Unicode::substr($value, 0, $suffix_length);
+    }
+    return $values;
+  }
+
 }
diff --git a/core/modules/field/src/Tests/Uri/UriItemTest.php b/core/modules/field/src/Tests/Uri/UriItemTest.php
index 46ffe0a..9dc50a2 100644
--- a/core/modules/field/src/Tests/Uri/UriItemTest.php
+++ b/core/modules/field/src/Tests/Uri/UriItemTest.php
@@ -68,6 +68,11 @@ public function testUriField() {
         'type' => 'uri',
       ])
       ->save();
+
+    // Test the generateSampleValue() method.
+    $entity = entity_create('entity_test');
+    $entity->$field_name->generateSampleItems();
+    $this->entityValidateAndSave($entity);
   }
 
 }