Q_OBJECT macro influences to QWidget's style sheet

I have encountered following issue:
Here is small example:

#ifndef EXAMPLE_H
#define EXAMPLE_H

#include <QWidget>


class Example : public QWidget
{
  Q_OBJECT

  public:
    explicit Example(QWidget *parent = 0);
};

#endif // EXAMPLE_H

#include "Example.h"


Example::Example(QWidget *parent)
  : QWidget(parent, Qt::Tool)
{
  setFixedSize(100, 100);
  setStyleSheet("border: 3px solid black; background-color: yellow;");
}

In such case instance of Example class have not applied style sheet for border (but it is ok with backgrond color).
But if I remove Q_OBJECT macro from header then all is ok - style sheet is fully applied to instance of Example widget.
Qt::Tool window flag is required. Without it, all works fine.

Full example is in attachment