Index: attachment_fu/test/processors/rmagick_test.rb
===================================================================
--- attachment_fu/test/processors/rmagick_test.rb	(revision 8)
+++ attachment_fu/test/processors/rmagick_test.rb	(working copy)
@@ -162,6 +162,7 @@
       assert_equal 'rails_thumb.png', attachment.thumbnails.first.filename
       assert_equal attachment.thumbnails.first.full_filename, attachment.full_filename(attachment.thumbnails.first.thumbnail),
         "#full_filename does not use thumbnail class' path."
+      assert_equal attachment.destroy attachment
     end
     
     test_against_subclass :test_should_use_thumbnail_subclass, ImageWithThumbsClassFileAttachment
Index: attachment_fu/lib/technoweenie/attachment_fu.rb
===================================================================
--- attachment_fu/lib/technoweenie/attachment_fu.rb	(revision 8)
+++ attachment_fu/lib/technoweenie/attachment_fu.rb	(working copy)
@@ -183,7 +183,7 @@
       
       # Returns true/false if an attachment is thumbnailable.  A thumbnailable attachment has an image content type and the parent_id attribute.
       def thumbnailable?
-        image? && respond_to?(:parent_id)
+        image? && respond_to?(:parent_id) && parent_id.nil?
       end
 
       # Returns the class used to create new thumbnails for this attachment.