diff -u b/core/modules/ckeditor/tests/src/FunctionalJavascript/CKEditorIntegrationTest.php b/core/modules/ckeditor/tests/src/FunctionalJavascript/CKEditorIntegrationTest.php
--- b/core/modules/ckeditor/tests/src/FunctionalJavascript/CKEditorIntegrationTest.php
+++ b/core/modules/ckeditor/tests/src/FunctionalJavascript/CKEditorIntegrationTest.php
@@ -65,10 +65,7 @@
       'field_storage' => $field_storage,
       'bundle' => 'page',
       'label' => 'Body',
-      'settings' => [
-        'display_summary' => TRUE,
-        'allowed_formats' => [],
-      ],
+      'settings' => ['display_summary' => TRUE],
       'required' => TRUE,
     ])->save();
 
@@ -76,7 +73,10 @@
       'field_storage' => $field_storage,
       'bundle' => 'page',
       'label' => 'Body',
-      'settings' => ['display_summary' => TRUE],
+      'settings' => [
+        'display_summary' => TRUE,
+        'allowed_formats' => [],
+      ],
       'required' => TRUE,
     ])->save();
 
diff -u b/core/modules/text/src/Plugin/Field/FieldType/TextItemBase.php b/core/modules/text/src/Plugin/Field/FieldType/TextItemBase.php
--- b/core/modules/text/src/Plugin/Field/FieldType/TextItemBase.php
+++ b/core/modules/text/src/Plugin/Field/FieldType/TextItemBase.php
@@ -31,15 +31,29 @@
     $element['allowed_formats'] = [
       '#type' => 'checkboxes',
       '#title' => $this->t('Allowed text formats'),
-      '#options' => $this->getProperties()['format']->getPossibleOptions(),
+      '#options' => $this->get('format')->getPossibleOptions(),
       '#default_value' => $settings['allowed_formats'],
       '#description' => $this->t('Select the allowed text formats. If no formats are selected, all available text formats will be displayed to the user.'),
+      '#element_validate' => [[static::class, 'validateAllowedFormats']]
     ];
 
     return $element;
   }
 
   /**
+   * Render API callback: Processes the allowed formats value.
+   *
+   * Ensure the element's value is an indexed array of selected format IDs.
+   *
+   * This function is assigned as an #element_validate callback in
+   * ::fieldSettingsForm().
+   */
+  public static function validateAllowedFormats(array &$element, FormStateInterface $form_state) {
+    $value = array_values(array_filter($element['#value']));
+    $form_state->setValueForElement($element, $value);
+  }
+
+  /**
    * {@inheritdoc}
    */
   public static function propertyDefinitions(FieldStorageDefinitionInterface $field_definition) {
diff -u b/core/modules/text/src/Plugin/Field/FieldWidget/TextareaWidget.php b/core/modules/text/src/Plugin/Field/FieldWidget/TextareaWidget.php
--- b/core/modules/text/src/Plugin/Field/FieldWidget/TextareaWidget.php
+++ b/core/modules/text/src/Plugin/Field/FieldWidget/TextareaWidget.php
@@ -34,18 +34,15 @@
    */
   public function formElement(FieldItemListInterface $items, $delta, array $element, array &$form, FormStateInterface $form_state) {
     $main_widget = parent::formElement($items, $delta, $element, $form, $form_state);
-    $allowed_formats_setting = $this->getFieldSetting('allowed_formats');
+    $allowed_formats = $this->getFieldSetting('allowed_formats');
 
     $element = $main_widget['value'];
     $element['#type'] = 'text_format';
     $element['#format'] = $items[$delta]->format;
     $element['#base_type'] = $main_widget['value']['#type'];
 
-    if (is_array($allowed_formats_setting)) {
-      $allowed_formats = array_filter($allowed_formats_setting);
-      if (!empty($allowed_formats) && !$this->isDefaultValueWidget($form_state)) {
-        $element['#allowed_formats'] = $allowed_formats;
-      }
+    if ($allowed_formats && !$this->isDefaultValueWidget($form_state)) {
+      $element['#allowed_formats'] = $allowed_formats;
     }
 
     return $element;
diff -u b/core/modules/text/src/Plugin/Field/FieldWidget/TextfieldWidget.php b/core/modules/text/src/Plugin/Field/FieldWidget/TextfieldWidget.php
--- b/core/modules/text/src/Plugin/Field/FieldWidget/TextfieldWidget.php
+++ b/core/modules/text/src/Plugin/Field/FieldWidget/TextfieldWidget.php
@@ -32,7 +32,7 @@
     $element['#format'] = isset($items[$delta]->format) ? $items[$delta]->format : NULL;
     $element['#base_type'] = $main_widget['value']['#type'];
 
-    if (!empty($allowed_formats) && !$this->isDefaultValueWidget($form_state)) {
+    if ($allowed_formats && !$this->isDefaultValueWidget($form_state)) {
       $element['#allowed_formats'] = $allowed_formats;
     }
 
diff -u b/core/modules/text/tests/src/Functional/TextFieldTest.php b/core/modules/text/tests/src/Functional/TextFieldTest.php
--- b/core/modules/text/tests/src/Functional/TextFieldTest.php
+++ b/core/modules/text/tests/src/Functional/TextFieldTest.php
@@ -216,7 +216,8 @@
     $this->drupalLogin($this->webUser);
     $this->drupalGet('entity_test/add');
     $this->assertFieldByName("{$field_name}[0][value]", NULL, 'Widget is displayed');
-    $this->assertFieldByName("{$field_name}[0][format]", NULL, 'Format selector is displayed');
+    $this->assertSession()->optionExists("{$field_name}[0][format]", $format1->id());
+    $this->assertSession()->optionExists("{$field_name}[0][format]", $format2->id());
 
     // Change field to allow only one format.
     $field->setSetting('allowed_formats', [$format1->id()]);
@@ -225,6 +226,15 @@
     $this->drupalGet('entity_test/add');
     $this->assertFieldByName("{$field_name}[0][value]", NULL, 'Widget is displayed');
     $this->assertNoFieldByName("{$field_name}[0][format]", NULL, 'Format selector is not displayed');
+
+    // Change field to allow all formats by configuring none as allowed.
+    $field->setSetting('allowed_formats', []);
+    $field->save();
+    $this->drupalGet('entity_test/add');
+    // We should see the 'format' selector again.
+    $this->assertFieldByName("{$field_name}[0][value]", NULL, 'Widget is displayed');
+    $this->assertSession()->optionExists("{$field_name}[0][format]", $format1->id());
+    $this->assertSession()->optionExists("{$field_name}[0][format]", $format2->id());
   }
 
   /**