changing attribute type

I have changed the type of an attribute as following : old one :

         <attribute qualifier="barcodeFormat" type="ABCFormatSet">
                     <modifiers optional="true" />
                     <persistence type="property" />
         /attribute>

New One:

         <attribute qualifier="barcodeFormat" type="ABCFormatList">
                     <modifiers optional="true" />
                     <persistence type="property" />
         </attribute>

I have performed ant clean all and update system. But still I am getting java.util.LinkedHashSet cannot be cast to java.util.List