diff --git a/wcfsetup/install/files/lib/data/attachment/Attachment.class.php b/wcfsetup/install/files/lib/data/attachment/Attachment.class.php
index 1636554105..32d9495a1a 100644
--- a/wcfsetup/install/files/lib/data/attachment/Attachment.class.php
+++ b/wcfsetup/install/files/lib/data/attachment/Attachment.class.php
@@ -260,7 +260,7 @@ public function getThumbnailLink($size = '')
         }
 
         $thumbnail = $file->getThumbnail($size !== 'tiny' ? '' : $size);
-        if ($this === null) {
+        if ($thumbnail === null) {
             return '';
         }