JAXB-ElipseLink: @XmlJavaTypeAdapter and the type-attribute

Question

I am using @XmlJavaTypeAdapter to marshal fields of type Map to XML. This results in EclipseLink-MOXy creating an xsi:type="<myValueType>"-attribute on the output xml-element. Upon validation the referenced type can of course not be found.

Is there any way of suppressing the generation of this attribute?

PS: An XmlAdapter-tag would be handy :)