Responsive theme and custom menu

I’ve got a custom menu called ‘Navigation’ which I’ve assigned as the primary menu in the theme. On a normal browser everything works fine. However when I switch to responsive design view and set the user-agent to be something like an iPhone, I see the menu as a dropdown with the correct pages in it, but there is an extra entry ‘Navigation’ – the menu itself. Is this correct behaviour – if not how do I fix it?

Regards
Alan