Force url ?amp=1

I need help to force all the AMP links to always use “?amp=1” instead of “/amp”.

I’m using for the filter below to accomplish it for <link rel=”amphtml”> in posts and pages (the code works) but in I’m homepage the <link rel=”amphtml”> and the link in the header of AMP pages the link uses “/amp”.

I already saved the Permalinks but it doesen’t works.

add_filter( 'amp_pre_get_permalink', 'my_amp_force_querystring_permalink', 10, 2 );

function my_amp_force_querystring_permalink( $permalink, $post_id ) {
    return add_query_arg( AMP_QUERY_VAR, 1, get_permalink( $post_id ) );
}