Prevent @JavaScript scripts to generate the async attribute

Hi all,
I am quite new to Vaadin Components and I’m trying to wrap an Alloy UI Component in Vaadin.
It seems, that everything works fine as long as I annotate the UI Class with

@JavaScript("https://cdn.alloyui.com/3.0.1/aui/aui-min.js")

But as soon as I move the Annotation down to Component Level it stops working.

package diagram;

import com.vaadin.annotations.JavaScript;
import com.vaadin.annotations.StyleSheet;
import com.vaadin.ui.AbstractJavaScriptComponent;

@JavaScript({ "https://cdn.alloyui.com/3.0.1/aui/aui-min.js", "diagram-builder.js" })
@StyleSheet({ "http://cdn.alloyui.com/2.5.0/aui-css/css/bootstrap.min.css", "styles.css" })
public class DiagramBuilder extends AbstractJavaScriptComponent {

    public DiagramBuilder() {
    }

}

The only difference (it seems) is that in this case the framework generates the following Element in the :

<script src="https://cdn.alloyui.com/3.0.1/aui/aui-min.js" type="text/javascript" async=""></script>

While when I annotate at UI Class level I get

<script type="text/javascript" src="https://cdn.alloyui.com/3.0.1/aui/aui-min.js"></script>

and the component is working as expected.

However as - at the moment we use this component only in one place we do not want the whole application to load the script.

Is there any way I can prevent the async being added? I found some information on ResourceLoader but this cannot be used in my DiagramBuilder class.

Any help is greatly appreciated.

Thanks,
Filip