Trace not working in OnResultExecuted() in MVC

Question

I'm trying to output to Trace.axd from an ASP.NET MVC app. I have traces in OnActionExecuting(), OnActionExecuted(), OnResultExecuting() and OnResultExecuted() and all of them output to Trace.axd except for OnResultExecuted().

For completeness' sake here's my code (exactly the same for OnActionX() ):

    protected override void OnResultExecuting(ResultExecutingContext filterContext)
    {
        resultStartTime = DateTime.Now;
        filterContext.HttpContext.Trace.Warn("OnResultExecuting: " + actionStartTime);
        base.OnResultExecuting(filterContext);
    }

    protected override void OnResultExecuted(ResultExecutedContext filterContext)
    {
        DateTime resultEndTime = DateTime.Now;
        filterContext.HttpContext.Trace.Warn("OnResultExecuted: " + resultEndTime);
        filterContext.HttpContext.Trace.Warn("OnResultExecuted - OnResultExecuting: " + (resultEndTime - resultStartTime).TotalSeconds);
        base.OnResultExecuted(filterContext);
    }

I am using ELMAH but I have disabled it and I still get the problem.