Problem with boolean type

[valerie . bauche]

I have the following schema element : 

  <xs:attribute name="mustUnderstand"> 
     <xs:simpleType>
              <xs:restriction base="xs:boolean">
           <xs:pattern value="0|1"/>
         </xs:restriction>
     </xs:simpleType>
  </xs:attribute>

Xbean generates the following accessors : 
    void setMustUnderstand(boolean mustUnderstand);
    boolean getMustUnderstand();

This result in an xml attribute with value "true" or "false" : it is not 
correct regarding the schema !

Is there anything to do to correct it?