get_post_meta not working on category.php

Question

I'm referencing an attached image in my header.php page which is displayed as a full screen background on my posts:

global $wp_query;
$page_id = $wp_query->get_queried_object_id();
$background_image = get_post_meta($page_id, 'mb_background_image', true);
$src = wp_get_attachment_image_src($background_image, 'full');

This works fine on single posts, but doesn't work when displaying just one post per page in category.php.

How can I fix this?

Thanks

Answer 1

The $page_id variable wasn't defined in category.php so I changed it to this.

$background_image = get_post_meta($post->ID, 'mb_background_image', true);