.../comment/lib/Drupal/comment/CommentViewBuilder.php     | 15 +++++++++++++++
 .../modules/comment/lib/Drupal/comment/Entity/Comment.php |  1 +
 .../lib/Drupal/comment/Tests/CommentCacheTagsTest.php     |  2 +-
 3 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/core/modules/comment/lib/Drupal/comment/CommentViewBuilder.php b/core/modules/comment/lib/Drupal/comment/CommentViewBuilder.php
index a2521ac..c1952a4 100644
--- a/core/modules/comment/lib/Drupal/comment/CommentViewBuilder.php
+++ b/core/modules/comment/lib/Drupal/comment/CommentViewBuilder.php
@@ -8,6 +8,7 @@
 namespace Drupal\comment;
 
 use Drupal\comment\Plugin\Field\FieldType\CommentItemInterface;
+use Drupal\Component\Utility\NestedArray;
 use Drupal\Core\Access\CsrfTokenGenerator;
 use Drupal\Core\Entity\Display\EntityViewDisplayInterface;
 use Drupal\Core\Entity\EntityInterface;
@@ -68,6 +69,20 @@ public function __construct(EntityTypeInterface $entity_type, EntityManagerInter
   }
 
   /**
+   * {@inheritdoc}
+   */
+  protected function getBuildDefaults(EntityInterface $entity, $view_mode, $langcode) {
+    $build = parent::getBuildDefaults($entity, $view_mode, $langcode);
+
+    // Comments are rendered as part of a node, so whenever the node is modified
+    // (whether that be a change in the path alias or even a new comment being
+    // posted), ensure that this rendered comment is invalidated also.
+    $build['#cache']['tags'] = NestedArray::mergeDeep($build['#cache']['tags'], $entity->getCommentedEntity()->getCacheTag());
+
+    return $build;
+  }
+
+  /**
    * Overrides Drupal\Core\Entity\EntityViewBuilder::buildComponents().
    *
    * In addition to modifying the content key on entities, this implementation
diff --git a/core/modules/comment/lib/Drupal/comment/Entity/Comment.php b/core/modules/comment/lib/Drupal/comment/Entity/Comment.php
index de10346..8507fe3 100644
--- a/core/modules/comment/lib/Drupal/comment/Entity/Comment.php
+++ b/core/modules/comment/lib/Drupal/comment/Entity/Comment.php
@@ -7,6 +7,7 @@
 
 namespace Drupal\comment\Entity;
 
+use Drupal\Component\Utility\NestedArray;
 use Drupal\Component\Utility\Number;
 use Drupal\Core\Entity\ContentEntityBase;
 use Drupal\comment\CommentInterface;
diff --git a/core/modules/comment/lib/Drupal/comment/Tests/CommentCacheTagsTest.php b/core/modules/comment/lib/Drupal/comment/Tests/CommentCacheTagsTest.php
index d12c6bb..be6b4af 100644
--- a/core/modules/comment/lib/Drupal/comment/Tests/CommentCacheTagsTest.php
+++ b/core/modules/comment/lib/Drupal/comment/Tests/CommentCacheTagsTest.php
@@ -81,7 +81,7 @@ protected function createEntity() {
    * Each comment must have a comment body, which always has a text format.
    */
   protected function getAdditionalCacheTagsForEntity(EntityInterface $entity) {
-    return array('filter_format:plain_text');
+    return array('entity_test:1', 'filter_format:plain_text');
   }
 
 }