Changing the size of default avatar

I am calling the wp_list_comments on one of my pages and trying to change the default avatar size which is output to the page.

I am using the following code but it is still not working.

$args = array ('post_type' => 'product');
$comments = get_comments( $args );
wp_list_comments( array( 'callback' => 'woocommerce_comments', 'avatar_size' => 512 ), $comments );

I am trying to change the size by passing the parameter ‘avatar size’