Styling QToolTip, removing corners, opacity not working.

[Enygma]

I have this:

QToolTip {
    border: 2px solid green;
    border-radius: 6px;
}

QToolTip {
    border: 2px solid green;
    border-radius: 6px;
}

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But I end up with some pretty disturbing corners with the background color where the border is rounded.

My question is: How can I get rid of them?

I tryed the opacity qss attirbute but it's not working, although in the documentation it says it works. Tried it with a simple example, no transparency there.

Bug?