Ошибка: 'resize_callbac': undeclared identifier. В чем может быть ошибка?

bool Window::init()
        {
            if (!glfwInit())
            {
                std::cout << "GLFW is not ok" << std::endl;
                glfwTerminate();
                return false;
            }
            window = glfwCreateWindow(width, height, name, NULL, NULL);
            glfwMakeContextCurrent(window);
            glfwSetWindowSizeCallback(window, resize_callbac);
            if (glewInit() != GLEW_OK)
            {
                std::cout << "GLEW is not ok" << std::endl;
                return false;
            }
            return true;
        }
        void Window::update()
        {
            glfwPollEvents();
            glfwSwapBuffers(window);
        }
        void Window::clear()
        {
            glClear(GL_COLOR_BUFFER_BIT);
        }
        void Window::render()
        {
            glBegin(GL_QUADS);
            glVertex2f(0.5f, 0.5f);
            glVertex2f(0.5f, -0.5f);
            glVertex2f(-0.5f, -0.5f);
            glVertex2f(-0.5f, 0.5f);
            glEnd();
        }
        void Window::mainLoop()
        {
            update();
            clear();
            render();
        }
        bool Window::closed()
        {
            return (glfwWindowShouldClose(window) == 1);
        }
        void resize_callbac(GLFWwindow* window, int width, int height)
        {
            glViewport(0, 0, width, height);