diff --git a/phpBB/phpbb/storage/controller/attachment.php b/phpBB/phpbb/storage/controller/attachment.php
index cbf798e953..c2b027d147 100644
--- a/phpBB/phpbb/storage/controller/attachment.php
+++ b/phpBB/phpbb/storage/controller/attachment.php
@@ -271,6 +271,16 @@ class attachment extends controller
 		return parent::handle($attachment['physical_filename']);
 	}
 
+	/**
+	 * {@inheritdoc}
+	 */
+	protected function prepare($file)
+	{
+		parent::prepare($file);
+
+		$this->response->setPivate();
+	}
+
 	/**
 	 * Handles authentication when downloading attachments from a post or topic
 	 *