diff --git a/src/Post/CommentPost.php b/src/Post/CommentPost.php
index af311b16967..400aa8a8fc7 100644
--- a/src/Post/CommentPost.php
+++ b/src/Post/CommentPost.php
@@ -169,7 +169,7 @@ public function setParsedContentAttribute($value)
      * @param ServerRequestInterface $request
      * @return string
      */
-    public function formatContent(ServerRequestInterface $request)
+    public function formatContent(ServerRequestInterface $request = null)
     {
         return static::$formatter->render($this->attributes['content'], $this, $request);
     }