diff -u b/core/modules/translation_entity/lib/Drupal/translation_entity/FieldTranslationSynchronizer.php b/core/modules/translation_entity/lib/Drupal/translation_entity/FieldTranslationSynchronizer.php
--- b/core/modules/translation_entity/lib/Drupal/translation_entity/FieldTranslationSynchronizer.php
+++ b/core/modules/translation_entity/lib/Drupal/translation_entity/FieldTranslationSynchronizer.php
@@ -9,6 +9,7 @@
 
 use Drupal\Core\Entity\EntityInterface;
 use Drupal\Core\Entity\EntityManager;
+use Drupal\Core\Entity\EntityNG;
 use Drupal\Core\Entity\Field\FieldInterface;
 
 /**
@@ -37,6 +38,12 @@
    * {@inheritdoc}
    */
   public function synchronizeFields(EntityInterface $entity, $sync_langcode, $original_langcode = NULL) {
+    // Field synchronization is only supported for NG entities.
+    $entity = $entity->getNGEntity();
+    if (!($entity instanceof EntityNG)) {
+      return;
+    }
+
     $translations = $entity->getTranslationLanguages();
 
     // If we have no information about what to sync to, if we are creating a new
@@ -120,7 +127,7 @@
     foreach ($translations as $langcode) {
       $entity->getTranslation($langcode)->{$field_name}->setValue(array());
     }
-    $entity->getTranslation($sync_langcode)->{$field_name}->setValue($source_items);
+    $entity->getTranslation($sync_langcode)->{$field_name}->setValue($source_items->getValue());
 
     // Update field translations.
     foreach ($translations as $langcode) {
@@ -160,7 +167,7 @@
           // If a synchronized column has changed or has been created from
           // scratch we need to override the full items array for all languages.
           elseif ($created) {
-            $new_values[$delta] = $source_items->offsetGet($delta);
+            $new_values[$delta] = $source_items->offsetGet($delta)->getValue();
           }
           // Otherwise the current item might have been reordered.
           elseif (isset($old_delta) && isset($new_delta)) {
@@ -169,7 +176,12 @@
             // the new values are at least propagated to all the translations.
             // If the value has only been reordered we just move the old one in
             // the new position.
-            $new_values[$delta] = isset($original_field_values[$langcode][$old_delta]) ? $original_field_values[$langcode][$old_delta] : $source_items[$new_delta];
+            if (isset($original_field_values[$langcode][$old_delta])) {
+              $new_values[$delta] = $original_field_values[$langcode][$old_delta];
+            }
+            else {
+              $new_values[$delta] = $source_items->offsetGet($new_delta)->getValue();
+            }
           }
         }
 
diff -u b/core/modules/translation_entity/lib/Drupal/translation_entity/Tests/EntityTranslationSyncImageTest.php b/core/modules/translation_entity/lib/Drupal/translation_entity/Tests/EntityTranslationSyncImageTest.php
--- b/core/modules/translation_entity/lib/Drupal/translation_entity/Tests/EntityTranslationSyncImageTest.php
+++ b/core/modules/translation_entity/lib/Drupal/translation_entity/Tests/EntityTranslationSyncImageTest.php
@@ -99,7 +99,6 @@
       'langcode' => $default_langcode,
     );
     $entity = entity_create($this->entityType, $values);
-//    $entity = entity_create($this->entityType, $values)->getBCEntity();
 
     // Create some file entities from the generated test files and store them.
     $values = array();
@@ -169,15 +168,15 @@
     // have been retained.
     $fids = array();
     foreach ($entity->{$this->fieldName} as $delta => $item) {
-      $value = $values[$default_langcode][$item['fid']];
+      $value = $values[$default_langcode][$item->fid];
       $source_item = $entity->getTranslation($langcode)->{$this->fieldName}->offsetGet($delta);
-      $assert = $item['fid'] == $source_item['fid'] && $item['alt'] == $value['alt'] && $item['title'] == $value['title'];
-      debug($source_item['fid'], 'source item fid');
+      $assert = $item->fid == $source_item->fid && $item->alt == $value['alt'] && $item->title == $value['title'];
+      debug($source_item->fid, 'source item fid');
       debug($item->fid, 'item fid');
       debug($item->getValue(), 'item');
       debug($value, 'value');
-      $this->assertTrue($assert, format_string('Field item @fid has been successfully synchronized.', array('@fid' => $item['fid'])));
-      $fids[$item['fid']] = TRUE;
+      $this->assertTrue($assert, format_string('Field item @fid has been successfully synchronized.', array('@fid' => $item->fid)));
+      $fids[$item->fid] = TRUE;
     }
 
     // Check that the dropped value is the right one.
@@ -204,11 +203,11 @@
       // When adding an item its value is copied over all the target languages,
       // thus in this case the source language needs to be used to check the
       // values instead of the target one.
-      $fid_langcode = $item['fid'] != $removed_fid ? $default_langcode : $langcode;
-      $value = $values[$fid_langcode][$item['fid']];
+      $fid_langcode = $item->fid != $removed_fid ? $default_langcode : $langcode;
+      $value = $values[$fid_langcode][$item->fid];
       $source_item = $entity->getTranslation($langcode)->{$this->fieldName}->offsetGet($delta);
-      $assert = $item['fid'] == $source_item['fid'] && $item['alt'] == $value['alt'] && $item['title'] == $value['title'];
-      $this->assertTrue($assert, format_string('Field item @fid has been successfully synchronized.', array('@fid' => $item['fid'])));
+      $assert = $item->fid == $source_item->fid && $item->alt == $value['alt'] && $item->title == $value['title'];
+      $this->assertTrue($assert, format_string('Field item @fid has been successfully synchronized.', array('@fid' => $item->fid)));
     }
   }