Page.slug() in blueprint doesn’t output anything

My simplified blueprint looks like this:

title: Example
        type: info
        text: {{ page.slug() }}

It doesn’t show the page slug in the info output. If I change it to page.title() it correctly shows the title. Is there anything I’m doing wrong? It used to work before; is this a bug? Or is the slug() method deprecated in 3.9.1?

Ah, damn, nevermind! It‘s always the same: I’m asking a question here and right after posting it, I figure it out myself. The brackets are apparently redundant/wrong, it works if I do {{ page.slug }}.