SFML sf::Clock issue

#include <SFML/Graphics.hpp>
#include "globals.h"
#include "ScreenGame.h"

int main()
{
    sf::RenderWindow window(sf::VideoMode(1280, 720), "SMASH");

    xScale = 1280.0f / window.getSize().x;
    yScale = 720.0f / window.getSize().y;

    screenManager.setScreen(new ScreenGame);

    sf::Clock frameClock;

    while (window.isOpen())
    {
        const double delta = frameClock.restart().asMilliseconds() / 16.66666667;

        sf::Event event;
        while (window.pollEvent(event))
        {
            if (event.type == sf::Event::Closed)
            {
                window.close();
            }
            else
            {
                screenManager.currentScreen->processEvent(window, event);
            }
        }

        screenManager.currentScreen->update(delta);
        screenManager.currentScreen->draw(window);
    }

    return 0;
}