diff --git a/core/lib/Drupal/Core/Entity/DatabaseStorageControllerNG.php b/core/lib/Drupal/Core/Entity/DatabaseStorageControllerNG.php
index 1048ca1..d436e49 100644
--- a/core/lib/Drupal/Core/Entity/DatabaseStorageControllerNG.php
+++ b/core/lib/Drupal/Core/Entity/DatabaseStorageControllerNG.php
@@ -156,19 +156,12 @@ protected function attachLoad(&$queried_entities, $load_revision = FALSE) {
     // Map the loaded stdclass records into entity objects and according fields.
     $queried_entities = $this->mapFromStorageRecords($queried_entities, $load_revision);
 
-    // Activate backward-compatibility mode to attach fields.
     if ($this->entityInfo['fieldable']) {
-      // Prepare BC compatible entities before passing them to the field API.
-      $bc_entities = array();
-      foreach ($queried_entities as $key => $entity) {
-        $bc_entities[$key] = $entity->getBCEntity();
-      }
-
       if ($load_revision) {
-        field_attach_load_revision($this->entityType, $bc_entities);
+        field_attach_load_revision($this->entityType, $queried_entities);
       }
       else {
-        field_attach_load($this->entityType, $bc_entities);
+        field_attach_load($this->entityType, $queried_entities);
       }
     }
 
@@ -419,7 +412,7 @@ protected function invokeHook($hook, EntityInterface $entity) {
       $function = 'field_attach_delete_revision';
     }
     if (!empty($this->entityInfo['fieldable']) && function_exists($function)) {
-      $function($entity->getBCEntity());
+      $function($entity);
     }
 
     // Invoke the hook.
diff --git a/core/lib/Drupal/Core/Entity/EntityFormControllerNG.php b/core/lib/Drupal/Core/Entity/EntityFormControllerNG.php
index ef9bc89..bfb41a8 100644
--- a/core/lib/Drupal/Core/Entity/EntityFormControllerNG.php
+++ b/core/lib/Drupal/Core/Entity/EntityFormControllerNG.php
@@ -27,7 +27,7 @@ public function form(array $form, array &$form_state, EntityInterface $entity) {
     // entity fields.
     $info = $entity->entityInfo();
     if (!empty($info['fieldable'])) {
-      field_attach_form($entity->getBCEntity(), $form, $form_state, $this->getFormLangcode($form_state));
+      field_attach_form($entity, $form, $form_state, $this->getFormLangcode($form_state));
     }
     return $form;
   }
@@ -42,7 +42,7 @@ public function validate(array $form, array &$form_state) {
     $info = $entity->entityInfo();
 
     if (!empty($info['fieldable'])) {
-      field_attach_form_validate($entity->getBCEntity(), $form, $form_state);
+      field_attach_form_validate($entity, $form, $form_state);
     }
 
     // @todo Remove this.
@@ -92,7 +92,7 @@ public function buildEntity(array $form, array &$form_state) {
 
     // Invoke field API for copying field values.
     if ($info['fieldable']) {
-      field_attach_extract_form_values($entity->getBCEntity(), $form, $form_state);
+      field_attach_extract_form_values($entity, $form, $form_state);
     }
     return $entity;
   }
diff --git a/core/modules/field/field.attach.inc b/core/modules/field/field.attach.inc
index de035d2..029bd4a 100644
--- a/core/modules/field/field.attach.inc
+++ b/core/modules/field/field.attach.inc
@@ -821,6 +821,9 @@ function _field_invoke_widget_target() {
  * @see field_form_set_state()
  */
 function field_attach_form(EntityInterface $entity, &$form, &$form_state, $langcode = NULL, array $options = array()) {
+  // Enable BC if necessary.
+  $entity = $entity->getBCEntity();
+
   // Set #parents to 'top-level' by default.
   $form += array('#parents' => array());
 
@@ -894,7 +897,11 @@ function field_attach_load($entity_type, $entities, $age = FIELD_LOAD_CURRENT, $
 
   // Assume all entities will need to be queried. Entities found in the cache
   // will be removed from the list.
-  $queried_entities = $entities;
+  $queried_entities = array();
+  foreach ($entities as $entity) {
+    // Enable BC if necessary.
+    $queried_entities[$entity->id()] = $entity->getBEntity();
+  }
 
   // Fetch available entities from cache, if applicable.
   if ($cache_read) {
@@ -1028,6 +1035,9 @@ function field_attach_load_revision($entity_type, $entities, $options = array())
  *   details.
  */
 function field_attach_validate(EntityInterface $entity, array $options = array()) {
+  // Enable BC if necessary.
+  $entity = $entity->getBCEntity();
+
   $errors = array();
   // Check generic, field-type-agnostic errors first.
   $null = NULL;
@@ -1077,6 +1087,9 @@ function field_attach_validate(EntityInterface $entity, array $options = array()
  *   details.
  */
 function field_attach_form_validate(EntityInterface $entity, $form, &$form_state, array $options = array()) {
+  // Enable BC if necessary.
+  $entity = $entity->getBCEntity();
+
   // Perform field_level validation.
   try {
     field_attach_validate($entity, $options);
@@ -1114,6 +1127,9 @@ function field_attach_form_validate(EntityInterface $entity, $form, &$form_state
  *   details.
  */
 function field_attach_extract_form_values(EntityInterface $entity, $form, &$form_state, array $options = array()) {
+  // Enable BC if necessary.
+  $entity = $entity->getBCEntity();
+
   // Extract field values from submitted values.
   field_invoke_method('extractFormValues', _field_invoke_widget_target(), $entity, $form, $form_state, $options);
 
@@ -1135,6 +1151,9 @@ function field_attach_extract_form_values(EntityInterface $entity, $form, &$form
  *   The entity with fields to process.
  */
 function field_attach_presave($entity) {
+  // Enable BC if necessary.
+  $entity = $entity->getBCEntity();
+
   _field_invoke('presave', $entity);
 
   // Let other modules act on presaving the entity.
@@ -1156,6 +1175,9 @@ function field_attach_presave($entity) {
  *   it leaves unspecified.
  */
 function field_attach_insert(EntityInterface $entity) {
+  // Enable BC if necessary.
+  $entity = $entity->getBCEntity();
+
   _field_invoke('insert', $entity);
 
   // Let any module insert field data before the storage engine, accumulating
@@ -1197,6 +1219,9 @@ function field_attach_insert(EntityInterface $entity) {
  *   The entity with fields to save.
  */
 function field_attach_update(EntityInterface $entity) {
+  // Enable BC if necessary.
+  $entity = $entity->getBCEntity();
+
   _field_invoke('update', $entity);
 
   // Let any module update field data before the storage engine, accumulating
@@ -1248,6 +1273,9 @@ function field_attach_update(EntityInterface $entity) {
  *   The entity whose field data to delete.
  */
 function field_attach_delete(EntityInterface $entity) {
+  // Enable BC if necessary.
+  $entity = $entity->getBCEntity();
+
   _field_invoke('delete', $entity);
 
   // Collect the storage backends used by the fields in the entities.
@@ -1281,6 +1309,9 @@ function field_attach_delete(EntityInterface $entity) {
  *   The entity with fields to save.
  */
 function field_attach_delete_revision(EntityInterface $entity) {
+  // Enable BC if necessary.
+  $entity = $entity->getBCEntity();
+
   _field_invoke('delete_revision', $entity);
 
   // Collect the storage backends used by the fields in the entities.
@@ -1505,6 +1536,9 @@ function field_attach_preprocess(EntityInterface $entity, $element, &$variables)
  *   The source language from which translate.
  */
 function field_attach_prepare_translation(EntityInterface $entity, $langcode, EntityInterface $source_entity, $source_langcode) {
+  // Enable BC if necessary.
+  $entity = $entity->getBCEntity();
+
   $options = array('langcode' => $langcode);
   // Copy source field values into the entity to be prepared.
   _field_invoke_default('prepare_translation', $entity, $source_entity, $source_langcode, $options);