treeMaker.removeClassTypeParameter(modifiedClazz,index) doesn't work correctly

I want to modify a class


Code:

public abstract class AbstractFacade<T> {

    private Class<T> entityClass;

    public AbstractFacade(Class<T> entityClass) {
        this.entityClass = entityClass;
    }
...
}



to

Code:

public abstract class AbstractFacade<T extends MyEntity> {

    private Class<T> entityClass;

    public AbstractFacade(Class<T> entityClass) {
        this.entityClass = entityClass;
    }




First I tried to delete the current type parameter with 

Code:
modifiedClazz=maker.removeClassTypeParameter(modifiedClazz,0);


and got 


Code:
public abstract class AbstractFacade> {// the > was not deleted
...
}



Then I tried

Code:
                            
TypeElement element = workingCopy.getElements().getTypeElement(entitiesPkg+".MyEntity");
ExpressionTree implementsClause = maker.QualIdent(element);
                            
List<ExpressionTree> bounds=new ArrayList<ExpressionTree>();                                    
TypeParameterTree tp=maker.TypeParameter("T", bounds);
tp=maker.addTypeParameterBound(tp, implementsClause);
 modifiedClazz=maker.addClassTypeParameter(modifiedClazz, tp);
      
//without the following line i got                    
//public abstract class AbstractFacade<T, T extends MyEntity>{                

modifiedClazz=maker.removeClassTypeParameter(modifiedClazz,0);
                           



It doesn't matter the index I use in removeClassTypeParameter (0 or 1) at the end  the result is  

Code:
public abstract class AbstractFacade<T> {



is there any workaround? am  I doing something wrong?

References:
http://bits.netbeans.org/dev/javadoc/org-netbeans-modules-java-source-base/allclasses-frame.html
http://wiki.netbeans.org/JavaHT_TreeMaker