NEW Backup (Beta) tar.gz in tar.gz

I am running a daily compressed backup.
Sometimes after backup process finished, i got the following warning from crondaemon.

tar: ./website.tar.gz: file changed as we read it

When i checked the content of the website.tar.gz file, there is another website.tar.gz file inside the compressed file.

This duplicates the backup file size.

The cause of the problem is this :
When tmp_bak folder is being compressed, the tar.gz file is also created in tmp_bak folder. When compresser detects the new file it interrputs the current process, and starts compressing all content again. This time it compresses the tmp_bak folder with the newly created tar.gz file.

I think compress command should be called with this parameter : --exclude=website.tar.gz
Or tar.gz file should be created out of the tmp_bak folder