use ->getOriginal() instead of ->original

src/Entity/FieldEncryptEntityType.php

@@ -4,6 +4,7 @@ declare(strict_types=1);
 
 namespace Drupal\field_encrypt\Entity;
 
+use Drupal\Component\Utility\DeprecationHelper;
 use Drupal\Core\Config\Entity\ConfigEntityBase;
 use Drupal\Core\Entity\Attribute\ConfigEntityType;
 use Drupal\Core\Entity\EntityStorageInterface;
@@ -117,7 +118,15 @@ class FieldEncryptEntityType extends ConfigEntityBase {
    */
   public function postSave(EntityStorageInterface $storage, $update = TRUE): void {
     parent::postSave($storage, $update);
-    if (!$update || $this->getBaseFields() !== $this->original->getBaseFields()) {
+
+    $original_entity = DeprecationHelper::backwardsCompatibleCall(
+      \Drupal::VERSION,
+      '11.2',
+      fn () => $this->getOriginal(),
+      fn () => $this->original,
+    );
+
+    if (!$update || $this->getBaseFields() !== $original_entity->getBaseFields()) {
       self::queueEntityUpdates($this->id());
     }
     // Update the field_encrypt module's state.