Define a JSON to XML namespace mapping
To fix this problem you need another annotation, @Mapped. You use the @Mapped annotation on your JAXB classes, on your JAX-RS resource method, or on the parameter you are unmarshalling import org.jboss.resteasy.annotations.providers.jaxb.json.Mapped; import org.jboss.resteasy.annotations.providers.jaxb.json.XmlNsMap; ... @GET @Produces("application/json") @Mapped(namespaceMap = { @XmlNsMap(namespace = "http://jboss.org/books", jsonName = "books") }) public Book get() {...}