Uploading - onProgress only called if files are big enough

flash help states this about the onProgress listener

In some cases, onProgress listeners are not invoked; for example, if the file being transmitted is very small, or if the upload or download happens very quickly.

I update a progress bar in my onProgress listener… so if I download files that are too small, my progress bar never changes.

listener.onProgress = function(file:FileReference, bytesLoaded:Number, bytesTotal:Number):Void {
    progress.mode = "manual";
    progress.setProgress(bytesLoaded, bytesTotal);
    trace("bytesLoaded: " + bytesLoaded + " bytesTotal: " + bytesTotal); 
}

How could I fix this?