Qt tool window resizable on Mac

I have a Qt window with the following flags:

Qt::CustomizeWindowHint
|Qt::Tool
|Qt::WindowCloseButtonHint
|Qt::WindowTitleHint
|Qt::MSWindowsFixedSizeDialogHint

On Mac, it has a resizable corner. How can I get rid of it? Specifying

setSizePolicy(QSizePolicy(QSizePolicy::F开发者_Python百科ixed, QSizePolicy::Fixed));

does not help. In fact, with the fixed-size policy the window acts weird when I try to resize - it disappears from foreground and becomes disabled for some reason.

I don't mind dropping to the native API level.

This is in the Qt FAQ.