#include <QTransform> fails

I am not able to compile a file with this single line in it:

#include <QTransform>

Errors are

include/QtGui/QPainterPath:1,
include/QtGui/qpainterpath.h|165 col 78| error: invalid use of incomplete type ‘class QTransform’
QList<QPolygonF> toSubpathPolygons(const QTransform &matrix = QTransform()) const;
In file included from include/QtGui/qpolygon.h:45,
include/QtCore/qpoint.h

note: forward declaration of ‘class QTransform’

It doesn't help to include QPainterPath earlier either,

To allow it to compile, you must:

class QPainterPath
#include <QPainterPath>
#include <QTransform>