"[node:termalias]" not working?

Hi,
hoping I am right here with my problem...

I'm using token "[node:termalias]" for setting breadcrumbs entrys via rules for threads in forum. According to documentation "[node:termalias]" should generate URL-alias of a term, which is exactly what I'm looking for.
In fact this produces only the term by itself, exactly the same as if I would use token "[node:term]".

Has anyone an idea?

Thanks in advance,
Ralf