QMessageBox::show problem

I have been playing with Qt for Webassembly quite a bit and recently I have noticed that the QMessageBox doesn't seem to update properly for smaller texts, for instance for the text:
"Are you sure you want to save the table?"

I get this:

While for the text:
"Are you sure you want to save the table? (this has a large text and because of that it works)"
I get this:

The first problem can be fixed by calling adjustSize() but that seems to be a workaround.

In the desktop it works as expected (Windows at least).

Attached is a small project that reproduces this issue.