---
title: Fixing AutoCAD error: ARX_ERROR:eNotThatKindOfClass
date: 2009-07-28
topics: AutoCAD
---

Some of our users have the old AutoCAD 2005 version, while a lucky few have the
newer 2009 version (licenses are danged expensive, you know). We had a case
where a drawing was being opened in AutoCAD 2009 and “saved-as” back to the 2004
format so the other users could open it. When attempting to perform commands on
the drawing in in the old 2005 version, however, the following error messages
would come up:

> `ARX_ERROR:eNotThatKindOfClass Command not allowed because drawing contains objects from a newer version of Architectural Desktop`

The solution, pointed to by various forum threads (such as [this
one](http://www.cadtutor.net/forum/showthread.php?s=d2bad05f1e697902b2a7024c33bf1285&t=16383)),
is to download and install the [Object Enabler
hotfix](http://usa.autodesk.com/adsk/servlet/ps/item?siteID=123112&id=9378493&linkID=9240617)
from the AutoDesk support site. Doing this immediately resolved the issue in our
case.

Another possible approach, in case that does not work for you, is to use the
`exporttoautocad` command instead of Save As - see [this
thread](http://discussion.autodesk.com/forums/message.jspa?messageID=5556678) on
the AutoDesk forums.