C++11: sleep_until() does not sleep at all

I'm trying to implement a simple game loop using this_thread::sleep_until(), but it doesn't seem to sleep at all. What could be the problem?

Here's the code:

// Duration of a single frame (1 / 60th of a second)
typedef std::chrono::duration<int, std::ratio<1, 60>> frame_duration;

// Typedef for fetching the delta time between two frames
typedef std::chrono::duration<float> fsec;

// Timer for a single second   
float secTimer = 0.f;

// Frame counter
int frames = 0;

auto start_time = std::chrono::steady_clock::now();

// Main loop
while(running) {
    // Get the delta since the last frame
    fsec = std::chrono::steady_clock::now() - start_time;
    float delta = fsec.count();

    // Print the FPS once every second (should be around 60)
    frames++;
    secTimer += delta;
    if(secTimer >= 1.f) {
        secTimer -= 1.f;
        std::cout << "FPS: " << frames << std::endl;
        frames = 0;
    }

    // Get the current frame's start time
    start_time = std::chrono::steady_clock::now();

    // *** Game logic goes here ***

    // Get the time until the next frame and sleep
    auto end_time = start_time + frame_duration(1);
    std::this_thread::sleep_until(end_time);
}