Filter collection by taxonomy of current entry

I am trying to set up a blog where at the bottom posts are shown that belong to the same categories as the one you are reading at that moment.

How do I do that. My current code is – in a shortened way – this:

{{ collection:blog paginate="true" limit="11" as="posts" id:isnt=id  taxonomy:category={{category}} }}
  {{ posts scope="grid" }}
    <a href="{{grid:url}}">{{grid:title}}</a>
  {{ /posts }}
{{ /collection:blog }}

This one doesn't work. It's not filtering the entries at att.