diff --git a/Models/NullComment.php b/Models/NullComment.php
index cd944ed..9a7b0fa 100755
--- a/Models/NullComment.php
+++ b/Models/NullComment.php
@@ -35,4 +35,12 @@ final class NullComment extends Comment
     {
         $this->id = $id;
     }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function jsonSerialize() : mixed
+    {
+        return ['id' => $this->id];
+    }
 }
diff --git a/Models/NullCommentList.php b/Models/NullCommentList.php
index 7cfdc11..a1eed7d 100755
--- a/Models/NullCommentList.php
+++ b/Models/NullCommentList.php
@@ -35,4 +35,12 @@ final class NullCommentList extends CommentList
     {
         $this->id = $id;
     }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function jsonSerialize() : mixed
+    {
+        return ['id' => $this->id];
+    }
 }
diff --git a/Models/NullCommentVote.php b/Models/NullCommentVote.php
index b9ec493..3cfd57c 100755
--- a/Models/NullCommentVote.php
+++ b/Models/NullCommentVote.php
@@ -35,4 +35,12 @@ final class NullCommentVote extends CommentVote
     {
         $this->id = $id;
     }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function jsonSerialize() : mixed
+    {
+        return ['id' => $this->id];
+    }
 }