Changing h2 to div footer widget

Hi, i've added the following code in an hook Element:

add_filter( 'generate_start_widget_title', 'generate_start_widget_title_wp' );
function generate_start_widget_title_wp() { return '<div class="widget-title">'; }

add_filter( 'generate_end_widget_title', 'generate_end_widget_title_wp' );
function generate_end_widget_title_wp() { return '</div>'; }

Unfortunately, it doesn't work. How can i get this to work?

Thanks!