How to set fix height on embedded image and keep width undefined

I’m trying to add an embedded image to a VerticalLayout. I want the height to be fixed and the width to scale proportional by not setting it. For FF this works perfect, but in IE the width gets set by Vaadin to the orignial size of the image. If I remove the width with the Developer Tool everything ist perfect. The image scales correctly. How can I prevent Vaadin to set a fixed size on the Embedded Image?

Here is the code:

VerticalLayout test = new VerticalLayout();
Embedded embedded = new Embedded("test",
		new ExternalResource(

Well, I figured out myself that this is a browser cache problem. If the IE already knows the image, the width of the original image is set ignoring that it should scale to the given height. The first call is ok, but after a refresh it is broken. I added a cache break to the url of the ExternalResource achieving that everything is alright if vaadin builds the page. The problem I do have now is, that if I make a reload in the browser, the vaadin state is the same and the page content doesn’t get refreshed. So the IE already knows the url to the image including the cache break and then the layout is broken again. Does anyone know how I can trigger a rebuild of the embedded image with a new timestamp when the browser gets refresehed?