Minor scrolling problem

I got a TextFlow with an image in the first line (before the first character) and the picture is cut off on the top. I checked the

_controller.verticalScrollPosition and it doesn't go below a specific number. The text is shown correctly so I assume that the images size is ignored and the top of the text is the lowest scroll position.

In the attached image you can see that the scroll bar shows that the position is above 0, but I can't scroll any higher.

Is this a bug or am I doing something wrong?

Thanks in advance