[Plugin: Simple Tags] st_tag_cloud show tags in specific category

I want to display tags from post in a specific category and I tried this code in my php sidebar widget.

<?php
st_tag_cloud(
‘category=Klients’
);
?>

But Simple Tags show tags from post in all my categories. Is it possible to only show tags from post in Klients category?

I have tried with category as text “Klients” or category id as a number “1” but I cant’t get it to work.