Index: wp-content/themes/twentythirteen/content.php
===================================================================
--- wp-content/themes/twentythirteen/content.php	(revision 23453)
+++ wp-content/themes/twentythirteen/content.php	(working copy)
@@ -10,7 +10,7 @@
 
 <article id="post-<?php the_ID(); ?>" <?php post_class(); ?>>
 	<header class="entry-header">
-		<?php if ( has_post_thumbnail() && ! is_single() && ! post_password_required() ) : ?>
+		<?php if ( has_post_thumbnail() && ! post_password_required() ) : ?>
 		<div class="entry-thumbnail">
 			<?php the_post_thumbnail(); ?>
 		</div>