Canceled task throws InvalidOperationException instead of TaskCanceledException

[n9]

Lets have the following code:

async void Main()
{
    try
    {
        var r = await Do();
        // do someting
    }
    catch (TaskCanceledException)
    {
        // do someting when canceled
    }
}

Task<int> Do()
{
    var tcs = new TaskCompletionSource<bool>();
    tcs.SetCanceled();
    return tcs.Task;
}

It works in .NET, however not in Saltarelle.
Since await in Saltarelle will throw InvalidOperationException (actually it won't compile, as there is no TaskCanceledException in Saltarelle).