The examples show posts (where the homepage is the blog list), but this works for any custom post type as well. I’ve used it forever; don’t remember where I got it from. This can go in your theme’s functions file or in a file in the mu-plugins folder.
// ADD "CURRENT" CLASS TO SPECIFIED POST TYPE
add_filter('nav_menu_css_class' , 'special_nav_class' , 10 , 2);
function special_nav_class($classes, $item){
if(is_singular('post') && $item->title == "Home"){
$classes[] = "current_page_ancestor";
}
if(is_archive('post') && $item->title == "Home"){
$classes[] = "current_page_ancestor";
}
if(is_paged('post') && $item->title == "Home"){
$classes[] = "current_page_ancestor";
}
return $classes;
}






