diff --git a/core/modules/media_library/src/Form/AddFormBase.php b/core/modules/media_library/src/Form/AddFormBase.php
index 507c99e725..a4571d1d72 100644
--- a/core/modules/media_library/src/Form/AddFormBase.php
+++ b/core/modules/media_library/src/Form/AddFormBase.php
@@ -20,6 +20,7 @@
 use Drupal\media\MediaInterface;
 use Drupal\media\MediaTypeInterface;
 use Drupal\media_library\Ajax\UpdateSelectionCommand;
+use Drupal\media_library\MediaLibraryState;
 use Drupal\media_library\MediaLibraryUiBuilder;
 use Drupal\media_library\OpenerResolverInterface;
 use Symfony\Component\DependencyInjection\ContainerInterface;
@@ -260,7 +261,7 @@ abstract protected function buildInputElement(array $form, FormStateInterface $f
    * @return array
    *   The element containing the required fields sub-form.
    */
-  protected function buildEntityFormElement(MediaInterface $media, array $form, FormStateInterface $form_state, int $delta, string $add_form_mode = 'media_library') {
+  protected function buildEntityFormElement(MediaInterface $media, array $form, FormStateInterface $form_state, int $delta, string $add_form_mode = MediaLibraryState::DEFAULT_FORM_MODE) {
     // We need to make sure each button has a unique name attribute. The default
     // name for button elements is 'op'. If the name is not unique, the
     // triggering element is not set correctly and the wrong media item is
diff --git a/core/modules/media_library/tests/modules/media_library_test_widget/config/schema/media_library_test_widget.schema.yml b/core/modules/media_library/tests/modules/media_library_test_widget/config/schema/media_library_test_widget.schema.yml
index 81186253e1..0e74387667 100644
--- a/core/modules/media_library/tests/modules/media_library_test_widget/config/schema/media_library_test_widget.schema.yml
+++ b/core/modules/media_library/tests/modules/media_library_test_widget/config/schema/media_library_test_widget.schema.yml
@@ -8,3 +8,6 @@ field.widget.settings.media_library_inception_widget:
       sequence:
         type: string
         label: 'Media type ID'
+    form_mode:
+      type: string
+      label: 'Form mode'
diff --git a/core/modules/media_library/tests/src/Kernel/MediaLibraryAddFormTest.php b/core/modules/media_library/tests/src/Kernel/MediaLibraryAddFormTest.php
index edea0e3e3a..b5a2734ad4 100644
--- a/core/modules/media_library/tests/src/Kernel/MediaLibraryAddFormTest.php
+++ b/core/modules/media_library/tests/src/Kernel/MediaLibraryAddFormTest.php
@@ -119,9 +119,7 @@ public function testMediaTypeAddForm() {
    *   The render array for the media library.
    */
   protected function buildLibraryUi($selected_type_id) {
-    // @todo where should this be pulled from? The field widget specifies.
-    $form_mode = 'media_library';
-    $state = MediaLibraryState::create('test', ['image', 'remote_video'], $selected_type_id, -1, [], $form_mode);
+    $state = MediaLibraryState::create('test', ['image', 'remote_video'], $selected_type_id, -1, [], $this->form_mode);
     return \Drupal::service('media_library.ui_builder')->buildUi($state);
   }
 
@@ -139,9 +137,7 @@ public function testFormStateValidation() {
    * Tests the validation of the selected type in the media library add form.
    */
   public function testSelectedTypeValidation() {
-    // @todo where should this be pulled from? The field widget specifies.
-    $form_mode = 'media_library';
-    $state = MediaLibraryState::create('test', ['image', 'remote_video', 'header_image'], 'header_image', -1, [], $form_mode);
+    $state = MediaLibraryState::create('test', ['image', 'remote_video', 'header_image'], 'header_image', -1, [], $this->form_mode);
     $form_state = new FormState();
     $form_state->set('media_library_state', $state);
     $this->expectException(\InvalidArgumentException::class);
diff --git a/core/modules/media_library/tests/src/Kernel/MediaLibraryStateTest.php b/core/modules/media_library/tests/src/Kernel/MediaLibraryStateTest.php
index 6b315dbd5f..bce48dbea2 100644
--- a/core/modules/media_library/tests/src/Kernel/MediaLibraryStateTest.php
+++ b/core/modules/media_library/tests/src/Kernel/MediaLibraryStateTest.php
@@ -25,7 +25,7 @@ class MediaLibraryStateTest extends KernelTestBase {
   /**
    * @var \Drupal\media\MediaTypeInterface|string
    */
-  protected static $form_mode = MediaLibraryState::DEFAULT_FORM_MODE;
+  protected $form_mode = MediaLibraryState::DEFAULT_FORM_MODE;
 
   /**
    * {@inheritdoc}