#include <QApplication>
#include <QMainWindow>
#include <QMenu>
#include <QToolBar>

class MainWindow : public QMainWindow
{
public:
  MainWindow() : QMainWindow()
  {
    QToolBar* toolBar = new QToolBar(this);

    QAction* actionWithMenu = new QAction("Action with menu", this);
    QMenu* menu = new QMenu(this);
    QAction* menuAction = new QAction("Menu action", this);
    menu->addAction(menuAction);
    actionWithMenu->setMenu(menu);

    QAction* actionWithoutMenu = new QAction("Action without menu", this);

    toolBar->addAction(actionWithMenu);
    toolBar->addAction(actionWithoutMenu);
    actionWithMenu->setEnabled(false);
    actionWithoutMenu->setEnabled(false);
    addToolBar(toolBar);

    setEnabled(false);
    setEnabled(true); // this line causes the issue
  }
protected:
  QSize sizeHint() const Q_DECL_OVERRIDE
  {
    return QSize(640, 480);
  }
};

int main(int argc, char *argv[])
{
  QApplication a(argc, argv);
  QMainWindow* window = new MainWindow();
  
  window->show();
  a.exec();
  return 0;
}