Not sprint while crouching?

So I'm in the early stages of making an FPS game and I've just implemented a sprint and crouch function (crouch only slows the player down at the moment). the functions are simply this:

private void sprintInput()
{

    if (Input.GetKeyDown(sprintKey))
    {           
        movementSpeed *= 2f;
    }
    if (Input.GetKeyUp(sprintKey))
    {          
        movementSpeed /= 2f;
    }
}


private void crouchInput()
{
    if (Input.GetKeyDown(crouchKey))
    {           
        movementSpeed /= 2f;
    }
    if (Input.GetKeyUp(crouchKey))
    {
        movementSpeed *= 2f;
    }
}

However written like this, they can obviously be activated both at the same time. But I want crouch to overwrite sprint. So if I use sprint and crouch at the same time, only crouch is activated. I've tried multiple methods but nothing works, I'm sure that I'm missing something painfully obvious, I just don't know what.