diff --git a/core/modules/comment/comment.module b/core/modules/comment/comment.module
index d34024b..b6483ee 100644
--- a/core/modules/comment/comment.module
+++ b/core/modules/comment/comment.module
@@ -1053,8 +1053,9 @@ function comment_entity_insert(EntityInterface $entity) {
       if ($entity instanceof EntityAuthorInterface) {
         $last_comment_uid = $entity->getAuthorId();
       }
-      else {
-        // Default to current user when entity does not have a uid property.
+      if (!isset($last_comment_uid)) {
+        // Default to current user when entity does not implements
+        // EntityAuthorInterface or author is not set.
         $last_comment_uid = \Drupal::currentUser()->id();
       }
       // Default to REQUEST_TIME when entity does not have a changed property.
diff --git a/core/modules/comment/lib/Drupal/comment/CommentStorageController.php b/core/modules/comment/lib/Drupal/comment/CommentStorageController.php
index de039f0..9141048 100644
--- a/core/modules/comment/lib/Drupal/comment/CommentStorageController.php
+++ b/core/modules/comment/lib/Drupal/comment/CommentStorageController.php
@@ -98,6 +98,14 @@ public function updateEntityStatistics(CommentInterface $comment) {
     else {
       // Comments do not exist.
       $entity = entity_load($comment->entity_type->value, $comment->entity_id->value);
+      if ($entity instanceof EntityAuthorInterface) {
+        $last_comment_uid = $entity->getAuthorId();
+      }
+      if (!isset($last_comment_uid)) {
+        // Default to current user when entity does not implements
+        // EntityAuthorInterface or author is not set.
+        $last_comment_uid = \Drupal::currentUser()->id();
+      }
       $this->database->update('comment_entity_statistics')
         ->fields(array(
           'cid' => 0,
@@ -108,7 +116,7 @@ public function updateEntityStatistics(CommentInterface $comment) {
           'last_comment_name' => '',
           // Get the user ID from the entity if it's set, or default to the
           // currently logged in user.
-          'last_comment_uid' => $entity instanceof EntityAuthorInterface ? $entity->getAuthorId() : \Drupal::currentUser()->id(),
+          'last_comment_uid' => $last_comment_uid,
         ))
         ->condition('entity_id', $comment->entity_id->value)
         ->condition('entity_type', $comment->entity_type->value)
diff --git a/core/modules/system/tests/modules/entity_test/lib/Drupal/entity_test/Entity/EntityTest.php b/core/modules/system/tests/modules/entity_test/lib/Drupal/entity_test/Entity/EntityTest.php
index e158fe9..fc7e1e1 100644
--- a/core/modules/system/tests/modules/entity_test/lib/Drupal/entity_test/Entity/EntityTest.php
+++ b/core/modules/system/tests/modules/entity_test/lib/Drupal/entity_test/Entity/EntityTest.php
@@ -170,4 +170,5 @@ public function setAuthorId($uid) {
     $this->set('user_id', $uid);
     return $this;
   }
+
 }