diff --git a/src/AppBundle/Controller/BlogController.php b/src/AppBundle/Controller/BlogController.php
index cf0ff4ae3..38c42b03c 100644
--- a/src/AppBundle/Controller/BlogController.php
+++ b/src/AppBundle/Controller/BlogController.php
@@ -94,7 +94,8 @@ public function commentNewAction(Request $request, Post $post)
     {
         $comment = new Comment();
         $comment->setAuthor($this->getUser());
-        $comment->setPost($post);
+
+        $post->addComment($comment);
 
         $form = $this->createForm(CommentType::class, $comment);
 
diff --git a/src/AppBundle/DataFixtures/ORM/PostFixtures.php b/src/AppBundle/DataFixtures/ORM/PostFixtures.php
index bc0553200..d441bdf53 100644
--- a/src/AppBundle/DataFixtures/ORM/PostFixtures.php
+++ b/src/AppBundle/DataFixtures/ORM/PostFixtures.php
@@ -66,10 +66,10 @@ public function load(ObjectManager $manager)
                 $comment->setAuthor($this->getReference('john-user'));
                 $comment->setPublishedAt(new \DateTime('now + '.($i + $j).'seconds'));
                 $comment->setContent($this->getRandomCommentContent());
-                $comment->setPost($post);
 
-                $manager->persist($comment);
                 $post->addComment($comment);
+
+                $manager->persist($comment);
             }
 
             $manager->persist($post);
diff --git a/src/AppBundle/Entity/Post.php b/src/AppBundle/Entity/Post.php
index 77e6f6bd1..dc1c2ed2a 100644
--- a/src/AppBundle/Entity/Post.php
+++ b/src/AppBundle/Entity/Post.php
@@ -203,13 +203,17 @@ public function getComments()
 
     public function addComment(Comment $comment)
     {
-        $this->comments->add($comment);
-        $comment->setPost($this);
+        if (!$this->comments->contains($comment)) {
+            $this->comments->add($comment);
+            $comment->setPost($this);
+        }
     }
 
     public function removeComment(Comment $comment)
     {
-        $this->comments->removeElement($comment);
+        if ($this->comments->removeElement($comment)) {
+            $comment->setPost(null);
+        }
     }
 
     public function getSummary()