Namespace defined through QName is not shown in xsi:type attribute leading to validation failure

Question

Here is my problem.

I have an xsd in which the need of polymorphism is answered by the use of xs:extension as follows:

<xs:complexType name="abstract_item" abstract="true">
    <xs:sequence>
        <xs:element name="blabla" type="xs:string" minOccurs="1" maxOccurs="1">
    </xs:sequence>  
</xs:complexType>

<xs:complexType name="itemA">
    <xs:complexContent>
        <xs:extension base="abstract_item">
            <xs:sequence>
                <xs:element name="blabla1" type="xs:string" minOccurs="0" maxOccurs="1">
            </xs:sequence>
        </xs:extension>
    </xs:complexContent>
</xs:complexType>

<xs:complexType name="itemB">
    <xs:complexContent>
        <xs:extension base="abstract_item">
            <xs:sequence>
                <xs:element name="blabla2" type="xs:date" minOccurs="0" maxOccurs="1">
            </xs:sequence>
        </xs:extension>
    </xs:complexContent>
</xs:complexType>

The JaxB classes appear to be correctly generated using xjc (two classes ItemA and ItemB extending an abstract class AbstractItem)

During marshaling a namespace is specified with QName (can't do without as it's part of the framework I'm obliged to use ...)

    Document document = DocumentBuilderFactory.newInstance().newDocumentBuilder().newDocument();
    JAXBContext context = JAXBContext.newInstance(retour.getClass());
    Marshaller marshaller = context.createMarshaller();
    QName qtag = new QName(retour.getNameSpace(), retour.getName());
    marshaller.marshal(new JAXBElement(qtag, retour.getClass(), retour), document);

    return document.getDocumentElement();

The generated XML looks something like :

<ns2:retour xmlns:ns2="https://my.custom.namespace">
  <items>
         <item xsi:type="itemA" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
            <blabla>test</blabla>
            <blabla1>A</blabla1>
         </item>
         <item xsi:type="itemB" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
            <blabla>test</blabla>
            <blabla2>01.01.2022</blabla2>
         </item>
     </items>
 </ns2:retour>

This xml is invalid with respect to the xsd because the types itemA and itemB are unknown. What is expected here is instead xsi:type="ns2:itemA" resp. xsi:type="ns2:itemB"

Is there an annotation that allows to force jaxb to annotate the xsi:type with the QName namespace given when marshaling?