diff --git a/core/lib/Drupal/Core/Entity/ContentEntityBase.php b/core/lib/Drupal/Core/Entity/ContentEntityBase.php
index cab168b2b2..721bd9c5cd 100644
--- a/core/lib/Drupal/Core/Entity/ContentEntityBase.php
+++ b/core/lib/Drupal/Core/Entity/ContentEntityBase.php
@@ -349,8 +349,15 @@ public function setRevisionTranslationAffected($affected) {
   /**
    * {@inheritdoc}
    */
+  public function setIsDefaultTranslation($is_default_translation) {
+    $this->isDefaultTranslation = $is_default_translation;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
   public function isDefaultTranslation() {
-    if (isset($this->isDefaultTranslation)) {
+    if ($this->isDefaultTranslation !== NULL) {
       return $this->isDefaultTranslation;
     }
     return $this->activeLangcode === LanguageInterface::LANGCODE_DEFAULT;
diff --git a/core/lib/Drupal/Core/Entity/ContentEntityStorageBase.php b/core/lib/Drupal/Core/Entity/ContentEntityStorageBase.php
index 815ea0bb73..210b7adaf6 100644
--- a/core/lib/Drupal/Core/Entity/ContentEntityStorageBase.php
+++ b/core/lib/Drupal/Core/Entity/ContentEntityStorageBase.php
@@ -485,13 +485,14 @@ protected function invokeFieldMethod($method, ContentEntityInterface $entity) {
     if ($method == 'postSave' && !empty($entity->original)) {
       $original_langcodes = array_keys($entity->original->getTranslationLanguages());
       foreach (array_diff($original_langcodes, $langcodes) as $removed_langcode) {
+        /** @var \Drupal\Core\Entity\ContentEntityInterface $translation */
         $translation = $entity->original->getTranslation($removed_langcode);
 
         // Fields may rely on the isDefaultTranslation() method to determine
         // what is going to be deleted - the whole entity or a particular
         // translation.
         if ($translation->isDefaultTranslation()) {
-          $translation->isDefaultTranslation = FALSE;
+          $translation->setIsDefaultTranslation(FALSE);
         }
 
         $fields = $translation->getTranslatableFields();
diff --git a/core/lib/Drupal/Core/TypedData/TranslatableInterface.php b/core/lib/Drupal/Core/TypedData/TranslatableInterface.php
index 5b57a8717f..1e648f8558 100644
--- a/core/lib/Drupal/Core/TypedData/TranslatableInterface.php
+++ b/core/lib/Drupal/Core/TypedData/TranslatableInterface.php
@@ -16,6 +16,18 @@
   public function language();
 
   /**
+   * Overrides isDefaultTranslation() result.
+   *
+   * @param bool|null $is_default_translation
+   *   If boolean value is passed, the value will override the result of
+   *   isDefaultTranslation() method. If NULL is passed, the default logic will
+   *   be used for determining the result.
+   *
+   * @internal
+   */
+  public function setIsDefaultTranslation($is_default_translation);
+
+  /**
    * Checks whether the translation is the default one.
    *
    * @return bool