diff --git a/core/lib/Drupal/Core/Entity/Entity/EntityViewDisplay.php b/core/lib/Drupal/Core/Entity/Entity/EntityViewDisplay.php
index c9a92b4..23ae3b3 100644
--- a/core/lib/Drupal/Core/Entity/Entity/EntityViewDisplay.php
+++ b/core/lib/Drupal/Core/Entity/Entity/EntityViewDisplay.php
@@ -227,7 +227,9 @@ public function buildMultiple(array $entities) {
     // Run field formatters.
     foreach ($this->getComponents() as $name => $options) {
       if ($formatter = $this->getRenderer($name)) {
-        $this->formatFieldMultiple($build_list, $entities, $formatter, $name);
+        foreach ($this->formatFieldMultiple($entities, $name, $formatter) as $key => $build) {
+          $build_list[$key][$name] = $build;
+        };
       }
     }
 
@@ -254,27 +256,23 @@ public function buildMultiple(array $entities) {
   /**
    * Formats a field for multiple entities.
    *
-   * @param array &$build_list
-   *   A reference to a renderable array, indexed by the same keys as the
-   *   $entities array parameter.
    * @param \Drupal\Core\Entity\FieldableEntityInterface[] $entities
    *   The entities being displayed.
-   * @param \Drupal\Core\Field\FormatterInterface $formatter
-   *   The field formatter to be used.
    * @param string $field_name
    *   The name of the field to be formatted.
-   * @param string $field_key
-   *   (optional) The key every field render array will be keyed with in the
-   *   build list. Defaults to the field name.
+   * @param \Drupal\Core\Field\FormatterInterface $formatter
+   *   The field formatter to be used.
+   *
+   * @return array
+   *   A renderable array, indexed by the same keys as the $entities array
+   *   parameter.
    */
-  protected function formatFieldMultiple(array &$build_list, array $entities, FormatterInterface $formatter, $field_name, $field_key = NULL) {
-    if (!isset($field_key)) {
-      $field_key = $field_name;
-    }
+  protected function formatFieldMultiple(array $entities, $field_name, FormatterInterface $formatter) {
+    $build_list = [];
 
     // Group items across all entities and pass them to the formatter's
     // prepareView() method.
-    $grouped_items = array();
+    $grouped_items = [];
     foreach ($entities as $index => $entity) {
       $items = $entity->get($field_name);
       $items->filterEmptyItems();
@@ -282,21 +280,17 @@ protected function formatFieldMultiple(array &$build_list, array $entities, Form
     }
     $formatter->prepareView($grouped_items);
 
+    // Then let the formatter build the output for each entity.
     foreach ($entities as $index => $entity) {
       /** @var \Drupal\Core\Field\FieldItemListInterface $items */
       $items = $grouped_items[$index];
-      // If a field key is explicitly not specified, it means we do not need the
-      // additional nesting level.
-      if ($field_key) {
-        $build = &$build_list[$index][$field_key];
-      }
-      else {
-        $build = &$build_list[$index];
-      }
-      // Then let the formatter build the output for each entity.
+      // @todo Will need to be adjusted after https://www.drupal.org/node/2099137
       $build = $formatter->view($items);
       $build['#access'] = $items->access('view');
+      $build_list[$index] = $build;
     }
+
+    return $build_list;
   }
 
   /**
@@ -311,8 +305,6 @@ public function buildField(FieldableEntityInterface $entity, FieldDefinitionInte
    * {@inheritdoc}
    */
   public function buildFieldMultiple(array $entities, FieldDefinitionInterface $field_definition, $type, $settings) {
-    $build_list = [];
-
     $options = [
       'field_definition' => $field_definition,
       'configuration' => array(
@@ -323,13 +315,12 @@ public function buildFieldMultiple(array $entities, FieldDefinitionInterface $fi
       ),
       'view_mode' => static::CUSTOM_MODE,
     ];
-
     /** @var \Drupal\Core\Field\FormatterInterface $formatter */
     if ($formatter = $this->pluginManager->getInstance($options)) {
-      $this->formatFieldMultiple($build_list, $entities, $formatter, $field_definition->getName(), FALSE);
+      return $this->formatFieldMultiple($entities, $field_definition->getName(), $formatter);
     }
 
-    return $build_list;
+    return [];
   }
 
   /**