Image and ExternalResource issue

Hi to all,

I’m using Vaadin 7.1.11 noticing a strange behavior when loading image with ExternalResource as image source.

My external resource path, points to a Servlet, used for serving image blobs in the response.
I’ve noticed that, when breakpointing the doGet method in this servlet, in Vaadin page appears loading indicator, but I’m not able to click anywhere in my application, the UI is completely blocked until all the images with the externalResource associated have been loaded.

Is this behavior correct?

Is there any way to make image src loading totally asynch, not causing the UI to freeze?