SQL & PL/SQL

Hi

I have the following code that errors out with the following error when i run it.

Error Message ORA-24813: cannot send or receive an unsupported LOB

My Code

declare

v_clob clob;

begin

   select DBMS_XMLQuery.GetXML('select * from dual') 
   into   v_clob
   from dual;
  dbms_output.put_line(v_clob);
Exception when others then 
   dbms_output.put_line(SQLERRM);
end;

does anyone what i'm missing.

Thanks