Menu causes W3C validation errors

Hi,

When I have the same menu for full (desktop) website and mobile version, W3C triggers a lot of validation errors as a result. Each menu item triggers an error like this:

Duplicate ID menu-item-xxxx
<div class=”menu-main-en-container”><ul id=”menu-main-en” class=”menu”><li id=”menu-item-xxxx” class=”menu-item menu-item-type-post_type menu-item-object-page current-menu-item page_item page-item-2 current_page_item menu-item-xxxx”>

Some sources suggest moving the ID to class to eliminate this problem, but I don’t know if it’s a good solution or if this even needs to be solved (i.e. if it can be safely ignored).

Please advise.

Thank you!