popup window doesn't show up as popup

Hi all,

I do have a page with a popup layout (which works fine).

Now I created an action button to a microflow, which shows the same page, so what I expect is that after clicking on the button, the page will still show up in a popup. Unfortunately this is not the case. The page is shown as a full page.

There are no property settings in the show page activity where I can change this behaviour. Is there a way to solve this?

thx. Jay