$custom_query->current_post not working!?!?

Hi everyone. I am designing a theme for WordPress and I need to create custom $wp_query calls in order to load in different post formats in different parts of the website. I write the following code:

<?php
$args = array(
   'post_type'=> 'post',
   'tax_query' => array(
   array(
      'taxonomy' => 'post_format',
      'field' => 'slug',
      'terms' => array( 'post-format-aside' )
   )
   )
);
$the_query = new WP_Query($args);
?>

<?php if ( $the_query->have_posts() ) : ?>

<?php while ( $the_query->have_posts() ) : $the_query->the_post(); ?>
<?php
   get_template_part( 'content-custom-posts', get_post_format() );
?>
<?php endwhile; ?>

My problem is that in the content-custom-posts.php I do a check

if($the_query->current_post == 0){...}
else {...}

However, for some reason even though the while loop loops through all my posts, the expression above ALWAYS evaluates to true, as if the current_post is not incrementing. I echoed $the_query->current_post and it gives back 0 1 2 3 4 … if I put it right before the get_template_part in the first code above, but DOES NOT RETURN ANYTHING if I echo it from within content-custom-posts.php

I searched all over the web and I cannot find a solution to my problem. Is my wp_query wrong for some reason? Because it works with $wp_query (default) but I need to do custom queries…

Thank you!