QColorDialog::open no-longer behaves as expected in Qt 5

Regression.

In Qt 4.8.4, the following code will produce a floating native colour picker dialog:

QColorDialog *colorDlg = new QColorDialog();
colorDlg->open();

But in Qt 5.0.0, it produces a non-native Qt color dialog instead.

The only way I've been able to the correct dialog back is to use QColorDialog::geColor() but this produces a modal dialog.