Popup Menu Keyboard Shortcut Mac issue

When adding a submenu with PopupMenu::Item to the main menubar on a mac, and setting it up with the setMacMainMenu() function call (so that it is similar to the standard functionality of a mac application) the keyboard shortcuts are not showing up in the menu. I am adding the item like this:

    PopupMenu::Item item {"item name"};
    item.isEnabled = true;
    item.shortcutKeyDescription = "c";
    item.action = []{};

This works when I am adding the menu to a window as a subcomponent. Is there something I am missing that needs to be added to the submenu when it is on a mac?