diff --git a/protected/humhub/docs/CHANGELOG.md b/protected/humhub/docs/CHANGELOG.md
index 17701cd6c0..56faa1ac65 100644
--- a/protected/humhub/docs/CHANGELOG.md
+++ b/protected/humhub/docs/CHANGELOG.md
@@ -1,10 +1,6 @@
 HumHub Changelog
 ================
 
-1.6.5 (Unreleased)
-------------------
-- Fix #4396: Submitting only picture in comment results in debug error.
-
 
 1.6.4 (Unreleased)
 ------------------
@@ -14,7 +10,7 @@ This release also brings a [security update](https://github.com/yiisoft/yii2/sec
 - Fix #4361: Added missing nonce attribute in inline marketplace script
 - Fix #4371: Word break issue in notification dropdown
 - Fix #4384: Upgrade to Yii 2.0.38
-
+- Fix #4396: Submitting only picture in comment results in debug error.
 
 1.6.3 (September 9, 2020)
 -----------------------
diff --git a/protected/humhub/modules/comment/controllers/CommentController.php b/protected/humhub/modules/comment/controllers/CommentController.php
index aa99fd3355..a8f2dda504 100644
--- a/protected/humhub/modules/comment/controllers/CommentController.php
+++ b/protected/humhub/modules/comment/controllers/CommentController.php
@@ -10,6 +10,7 @@ namespace humhub\modules\comment\controllers;
 
 use humhub\components\Controller;
 use humhub\libs\Helpers;
+use humhub\modules\comment\models\forms\CommentForm;
 use humhub\modules\comment\Module;
 use humhub\modules\content\components\ContentActiveRecord;
 use humhub\modules\content\models\Content;
@@ -21,7 +22,6 @@ use humhub\components\behaviors\AccessControl;
 use humhub\modules\comment\models\Comment;
 use humhub\modules\comment\widgets\Comment as CommentWidget;
 use humhub\modules\comment\widgets\ShowMore;
-use yii\web\BadRequestHttpException;
 use yii\web\ForbiddenHttpException;
 
 /**
@@ -130,22 +130,15 @@ class CommentController extends Controller
         }
 
         return Comment::getDb()->transaction(function ($db) {
-            $message = Yii::$app->request->post('message');
-            $files = Yii::$app->request->post('fileList');
 
-            if (empty(trim($message)) && empty($files)) {
-                throw new BadRequestHttpException(Yii::t('CommentModule.base', 'The comment must not be empty!'));
+            $form = new CommentForm($this->target);
+
+            if ($form->load(Yii::$app->request->post()) && $form->validate()) {
+                $comment = $form->save();
+                return $this->renderAjaxContent(CommentWidget::widget(['comment' => $comment]));
+            } else {
+                return false;
             }
-
-            $comment = new Comment(['message' => $message]);
-            $comment->setPolyMorphicRelation($this->target);
-            $comment->save();
-            $comment->fileManager->attach($files);
-
-            // Reload comment to get populated created_at field
-            $comment->refresh();
-
-            return $this->renderAjaxContent(CommentWidget::widget(['comment' => $comment]));
         });
     }
 
@@ -154,14 +147,26 @@ class CommentController extends Controller
     {
         $comment = Comment::findOne(['id' => Yii::$app->request->get('id')]);
 
+        // Find all file attached to this comment
+        $files = $comment->fileManager->find()->asArray()->all();
+        $fileList = [];
+        $i = 0;
+
+        // Fill up files array
+        foreach ($files as $file) {
+            $fileList[$i] = $file['guid'];
+            $i++;
+        }
+
         if (!$comment->canEdit()) {
             throw new HttpException(403, Yii::t('CommentModule.base', 'Access denied!'));
         }
 
-        if ($comment->load(Yii::$app->request->post()) && $comment->save()) {
+        $form = new CommentForm($this->target, $fileList);
 
-            // Reload comment to get populated updated_at field
-            $comment = Comment::findOne(['id' => $comment->id]);
+        if ($form->load(Yii::$app->request->post(), '') && $form->validate()) {
+
+            $comment = $form->update($comment);
 
             return $this->renderAjaxContent(CommentWidget::widget([
                 'comment' => $comment,
diff --git a/protected/humhub/modules/comment/models/Comment.php b/protected/humhub/modules/comment/models/Comment.php
index f9e856fddf..96f405fc99 100644
--- a/protected/humhub/modules/comment/models/Comment.php
+++ b/protected/humhub/modules/comment/models/Comment.php
@@ -57,9 +57,6 @@ class Comment extends ContentAddonActiveRecord implements ContentOwner
     {
         return [
             [['message'], 'safe'],
-            [['message'], 'required', 'when' => function ($comment) {
-                return !$comment->fileManager->find()->exists();
-            }],
         ];
     }
 
diff --git a/protected/humhub/modules/comment/models/forms/CommentForm.php b/protected/humhub/modules/comment/models/forms/CommentForm.php
new file mode 100644
index 0000000000..26ce05f23c
--- /dev/null
+++ b/protected/humhub/modules/comment/models/forms/CommentForm.php
@@ -0,0 +1,122 @@
+<?php
+
+namespace humhub\modules\comment\models\forms;
+
+use humhub\modules\comment\models\Comment;
+use humhub\modules\content\components\ContentActiveRecord;
+use Yii;
+use yii\web\ServerErrorHttpException;
+
+/**
+ * CommentForm
+ * @package humhub\modules\comment\models\forms
+ *
+ * @since 0.5
+ */
+class CommentForm extends yii\base\Model
+{
+    public $message;
+    public $fileList;
+
+    /**
+     * @var Comment|ContentActiveRecord The model to comment
+     */
+    public $target;
+
+    public function __construct($target, $fileList = null)
+    {
+        $this->target = $target;
+        $this->fileList = $fileList;
+        parent::__construct();
+    }
+
+    /**
+     * @return array validation rules for model attributes.
+     */
+    public function rules()
+    {
+        return [
+            [['message'], 'safe'],
+            [['message'], 'required', 'isEmpty' => function ($message) {
+                $hasFile = !is_null($this->fileList) && !empty($this->fileList) ? true : false;
+
+                //check if message empty and attached file exists
+                if (empty($message) && !$hasFile) {
+                    throw new ServerErrorHttpException(Yii::t('CommentModule.base', 'The comment must not be empty!'));
+                }
+            }],
+            [['fileList'], 'safe'],
+        ];
+    }
+
+    /**
+     * @inheritDoc
+     */
+    public function load($data, $formName = null)
+    {
+        // When user updates comment $data contain 'Comment', otherwise not
+        if (isset($data['Comment'])) {
+            $data['message'] = $data['Comment']['message'];
+            unset($data['Comment']);
+        }
+
+        return parent::load($data, $formName);
+    }
+
+    /**
+     * @inheritDoc
+     */
+    public function formName()
+    {
+        return '';
+    }
+
+    /**
+     * Updates the form
+     *
+     * @param Comment $comment
+     * @return Comment|boolean
+     */
+    public function update($comment)
+    {
+
+        $comment->message = $this->message;
+        $comment->setPolyMorphicRelation($this->target);
+
+        //check if model saved
+        if (!$comment->save()) {
+            return false;
+        }
+
+        $comment->fileManager->attach($this->fileList);
+
+        // Reload comment to get populated created_at field
+        $comment->refresh();
+        return $comment;
+    }
+
+
+    /**
+     * Saves the form
+     *
+     * @return Comment|boolean
+     */
+    public function save()
+    {
+
+        $comment = new Comment(['message' => $this->message]);
+        $comment->setPolyMorphicRelation($this->target);
+
+        //check if model saved
+        if (!$comment->save()) {
+            return false;
+        }
+
+        $comment->fileManager->attach($this->fileList);
+
+        // Reload comment to get populated created_at field
+        $comment->refresh();
+        return $comment;
+    }
+
+}