trouble calling different header.php for home.php

I’m making a site that uses the same header.php for all pages except the blog/home.php. For this, I’ve created blog-header.php and am attempting to call it using the following:

<?php if( is_page(15) ) {
echo get_template_part( 'blog', 'header' );}
else {
echo get_header(); } ?>

However, it doesn’t seem to be working. Any ideas on why that may be?

(Unfortunately, the site isn’t live yet otherwise I’d provide a link.)