fieldableentityinterface.patch

diff --git a/src/Element/InlineEntityForm.php b/src/Element/InlineEntityForm.php
index 0fbe233..f47e2de 100644
--- a/src/Element/InlineEntityForm.php
+++ b/src/Element/InlineEntityForm.php
@@ -8,6 +8,7 @@ use Drupal\Core\Render\Element;
 use Drupal\Core\Render\Element\RenderElement;
 use Drupal\inline_entity_form\ElementSubmit;
 use Drupal\inline_entity_form\TranslationHelper;
+use Drupal\Core\Entity\ContentEntityInterface;
 
 /**
  * Provides an inline entity form element.
@@ -128,9 +129,12 @@ class InlineEntityForm extends RenderElement {
         $entity_form['#op'] = $entity_form['#entity']->isNew() ? 'add' : 'edit';
       }
     }
-    // Prepare the entity form and the entity itself for translating.
-    $entity_form['#entity'] = TranslationHelper::prepareEntity($entity_form['#entity'], $form_state);
-    $entity_form['#translating'] = TranslationHelper::isTranslating($form_state) && $entity_form['#entity']->isTranslatable();
+
+    if ($entity_form['#entity'] instanceof ContentEntityInterface) {
+      // Prepare the entity form and the entity itself for translating.
+      $entity_form['#entity'] = TranslationHelper::prepareEntity($entity_form['#entity'], $form_state);
+      $entity_form['#translating'] = TranslationHelper::isTranslating($form_state) && $entity_form['#entity']->isTranslatable();
+    }
 
     $inline_form_handler = static::getInlineFormHandler($entity_form['#entity_type']);
     $entity_form = $inline_form_handler->entityForm($entity_form, $form_state);
diff --git a/src/Form/EntityInlineForm.php b/src/Form/EntityInlineForm.php
index 1ff5073..fef1148 100644
--- a/src/Form/EntityInlineForm.php
+++ b/src/Form/EntityInlineForm.php
@@ -2,7 +2,7 @@
 
 namespace Drupal\inline_entity_form\Form;
 
-use Drupal\Core\Entity\ContentEntityInterface;
+use Drupal\Core\Entity\FieldableEntityInterface;
 use Drupal\Core\Entity\Entity\EntityFormDisplay;
 use Drupal\Core\Entity\EntityInterface;
 use Drupal\Core\Entity\EntityFieldManagerInterface;
@@ -279,12 +279,12 @@ class EntityInlineForm implements InlineFormInterface {
    *
    * @param array $entity_form
    *   The entity form.
-   * @param \Drupal\Core\Entity\ContentEntityInterface $entity
+   * @param \Drupal\Core\Entity\FieldableEntityInterface $entity
    *   The entity.
    * @param \Drupal\Core\Form\FormStateInterface $form_state
    *   The current state of the form.
    */
-  protected function buildEntity(array $entity_form, ContentEntityInterface $entity, FormStateInterface $form_state) {
+  protected function buildEntity(array $entity_form, FieldableEntityInterface $entity, FormStateInterface $form_state) {
     $form_display = $this->getFormDisplay($entity, $entity_form['#form_mode']);
     $form_display->extractFormValues($entity, $entity_form, $form_state);
     // Invoke all specified builders for copying form values to entity fields.
@@ -330,7 +330,7 @@ class EntityInlineForm implements InlineFormInterface {
   /**
    * Gets the form display for the given entity.
    *
-   * @param \Drupal\Core\Entity\ContentEntityInterface $entity
+   * @param \Drupal\Core\Entity\FieldableEntityInterface $entity
    *   The entity.
    * @param string $form_mode
    *   The form mode.
@@ -338,7 +338,7 @@ class EntityInlineForm implements InlineFormInterface {
    * @return \Drupal\Core\Entity\Display\EntityFormDisplayInterface
    *   The form display.
    */
-  protected function getFormDisplay(ContentEntityInterface $entity, $form_mode) {
+  protected function getFormDisplay(FieldableEntityInterface $entity, $form_mode) {
     return EntityFormDisplay::collectRenderDisplay($entity, $form_mode);
   }