.../Field/FieldFormatter/CommentDefaultFormatter.php   | 12 ++++++++++++
 .../FieldFormatter/EntityReferenceEntityFormatter.php  | 18 +++++++-----------
 2 files changed, 19 insertions(+), 11 deletions(-)

diff --git a/core/modules/comment/lib/Drupal/comment/Plugin/Field/FieldFormatter/CommentDefaultFormatter.php b/core/modules/comment/lib/Drupal/comment/Plugin/Field/FieldFormatter/CommentDefaultFormatter.php
index 154edf6..eba2654 100644
--- a/core/modules/comment/lib/Drupal/comment/Plugin/Field/FieldFormatter/CommentDefaultFormatter.php
+++ b/core/modules/comment/lib/Drupal/comment/Plugin/Field/FieldFormatter/CommentDefaultFormatter.php
@@ -145,6 +145,18 @@ public function viewElements(FieldItemListInterface $items) {
           if ($this->getSetting('pager_id')) {
             $build['pager']['#element'] = $this->getSetting('pager_id');
           }
+          // Entity field formatters are run during the #pre_render phase of
+          // rendering an entity. Therefore, that is the time when this function
+          // runs. After that #pre_render callback, all cache tags must be
+          // available. However, this field formatter is highly exceptional: it
+          // renders *other* entities (i.e. entities within an entity). Those
+          // other entities come with their own #pre_render callback that must
+          // be called in order for the cache tags associated with them to be
+          // included with  those of the main entity. Hence we must render the
+          // the other entities *immediately* (which includes running their
+          // #pre_render callback), otherwise their associated cache tags won't
+          // bubble up.
+          drupal_render($build, TRUE);
           $output['comments'] = $build;
         }
       }
diff --git a/core/modules/entity_reference/lib/Drupal/entity_reference/Plugin/Field/FieldFormatter/EntityReferenceEntityFormatter.php b/core/modules/entity_reference/lib/Drupal/entity_reference/Plugin/Field/FieldFormatter/EntityReferenceEntityFormatter.php
index d8d9d41..a7e19f6 100644
--- a/core/modules/entity_reference/lib/Drupal/entity_reference/Plugin/Field/FieldFormatter/EntityReferenceEntityFormatter.php
+++ b/core/modules/entity_reference/lib/Drupal/entity_reference/Plugin/Field/FieldFormatter/EntityReferenceEntityFormatter.php
@@ -93,8 +93,6 @@ public function viewElements(FieldItemListInterface $items) {
       }
 
       if (!empty($item->target_id)) {
-        $elements[$delta] = entity_view($item->entity, $view_mode, $item->getLangcode());
-
         // Entity field formatters are run during the #pre_render phase of
         // rendering an entity. Therefore, that is the time when this function
         // runs. After that #pre_render callback, all cache tags must be
@@ -102,15 +100,13 @@ public function viewElements(FieldItemListInterface $items) {
         // renders *another* entity (i.e. an entity within an entity). That
         // other entity comes with its own #pre_render callback that must be
         // called in order for the cache tags associated with that other entity
-        // to be included with those of the main entity. Hence we must run the
-        // other entity's #pre_render callbacks *immediately*, otherwise its
-        // associated cache tags won't bubble up correctly.
-        if (isset($elements[$delta]['#pre_render'])) {
-          foreach ($elements[$delta]['#pre_render'] as $callable) {
-            $elements[$delta] = call_user_func($callable, $elements[$delta]);
-          }
-        }
-        unset($elements[$delta]['#pre_render']);
+        // to be included with those of the main entity. Hence we must render
+        // the other entity *immediately* (which includes running its
+        // #pre_render callbacks), otherwise its associated cache tags won't
+        // bubble up.
+        $referenced_entity_build = entity_view($item->entity, $view_mode, $item->getLangcode());
+        drupal_render($referenced_entity_build, TRUE);
+        $elements[$delta] = $referenced_entity_build;
 
         if (empty($links) && isset($result[$delta][$target_type][$item->target_id]['links'])) {
           // Hide the element links.