diff --git a/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/StringItem.php b/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/StringItem.php
index f7ef6e402f0..8641fa22329 100644
--- a/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/StringItem.php
+++ b/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/StringItem.php
@@ -91,14 +91,21 @@ class StringItem extends FieldItemBase {
   public static function generateSampleValue(FieldDefinitionInterface $field_definition) {
     $random = new Random();
     $max = $field_definition->getSetting('max_length');
-    $values['value'] = $random->word(mt_rand(1, $max));
+
+    if ($max) {
+      $values['value'] = $random->word(mt_rand(1, $max));
+    }
+    else {
+      $values['value'] = $random->paragraphs();
+    }
+
     return $values;
   }
 
   /**
    * {@inheritdoc}
    */
-  public function settingsForm(array &$form, FormStateInterface $form_state, $has_data) {
+  public function storageSettingsForm(array &$form, FormStateInterface $form_state, $has_data) {
     $element = array();
 
     $element['max_length'] = array(
diff --git a/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/StringLongItem.php b/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/StringLongItem.php
index 30a9df0f34a..1a17ede6390 100644
--- a/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/StringLongItem.php
+++ b/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/StringLongItem.php
@@ -8,6 +8,7 @@
 namespace Drupal\Core\Field\Plugin\Field\FieldType;
 
 use Drupal\Core\Field\FieldStorageDefinitionInterface;
+use Drupal\Core\Form\FormStateInterface;
 
 /**
  * Defines the 'string_long' field type.
@@ -22,6 +23,15 @@ use Drupal\Core\Field\FieldStorageDefinitionInterface;
  */
 class StringLongItem extends StringItem {
 
+  /**
+   * {@inheritdoc}
+   */
+  public static function defaultStorageSettings() {
+    $settings = parent::defaultStorageSettings();
+    unset($settings['max_length']);
+    return $settings;
+  }
+
   /**
    * {@inheritdoc}
    */
@@ -36,4 +46,13 @@ class StringLongItem extends StringItem {
     );
   }
 
+  /**
+   * {@inheritdoc}
+   */
+  public function storageSettingsForm(array &$form, FormStateInterface $form_state, $has_data) {
+    $element = parent::storageSettingsForm($form, $form_state, $has_data);
+    unset($element['max_length']);
+    return $element;
+  }
+
 }