diff --git a/src/Attachment.php b/src/Attachment.php
index c2c29ab..364609c 100644
--- a/src/Attachment.php
+++ b/src/Attachment.php
@@ -386,7 +386,7 @@ public function originalFilename()
      */
     public function getInstanceClass()
     {
-        return get_class($this->instance);
+        return is_null($this->instance) ? get_class() : get_class($this->instance);
     }
 
     /**