Enable Folder Creation when create list Definition by Visual Studio

Hello,

•   I have created a List definition in Visual Studio .
• In the element.xml of List Definition : 

             <ListTemplate
                 Name="ArticlesList"
                 Type="10000"
                  BaseType="0"
                 DisplayName="Article List"
                Description="Article List"
                 Image="/_layouts/images/itgen.png" 
                 FolderCreation="TRUE"/>

• When I open The list . The folder creation is still disabled ? so what is wrong?

ASk