Index: wp-content/themes/twentyfourteen/inc/template-tags.php
===================================================================
--- wp-content/themes/twentyfourteen/inc/template-tags.php	(revision 30042)
+++ wp-content/themes/twentyfourteen/inc/template-tags.php	(working copy)
@@ -189,12 +189,12 @@
 
 	<?php else : ?>
 
-	<a class="post-thumbnail" href="<?php the_permalink(); ?>">
+	<a class="post-thumbnail" href="<?php the_permalink(); ?>" aria-hidden="true">
 	<?php
 		if ( ( ! is_active_sidebar( 'sidebar-2' ) || is_page_template( 'page-templates/full-width.php' ) ) ) {
 			the_post_thumbnail( 'twentyfourteen-full-width' );
 		} else {
-			the_post_thumbnail();
+			the_post_thumbnail( 'post-thumbnail', array( 'alt'=>get_the_title() ) );
 		}
 	?>
 	</a>