diff --git a/Services/Mail/classes/class.ilMailAttachmentTableGUI.php b/Services/Mail/classes/class.ilMailAttachmentTableGUI.php
index 20e64f00549b..fb6bf7f9c6ff 100644
--- a/Services/Mail/classes/class.ilMailAttachmentTableGUI.php
+++ b/Services/Mail/classes/class.ilMailAttachmentTableGUI.php
@@ -93,7 +93,7 @@ protected function formatValue($column, $value)
                 return ilDatePresentation::formatDate(new ilDateTime($value, IL_CAL_UNIX));
 
             case 'filesize':
-                return ilUtil::formatSize($value);
+                return ilUtil::formatSize($value, 'long');
 
             default:
                 return $value;