[TYPO3] Problem with RealURL and preview from backend

[Peter Kraume]

Hi all,

I've configured RealURL so that every URL gets a country prefix like that:
http://www.domain.tld/de/page.html

That works perfectly, but when I use the preview function of the backend 
then the country prefix is missing in the URLs:
http://www.domain.tld/page.html

What can I do to make the backend previews work like the "normal website"?

Regards,
Peter