Index: wp-includes/widgets/class-wp-widget-recent-posts.php
===================================================================
--- wp-includes/widgets/class-wp-widget-recent-posts.php	(revision 36445)
+++ wp-includes/widgets/class-wp-widget-recent-posts.php	(working copy)
@@ -78,7 +78,7 @@
 		<ul>
 		<?php while ( $r->have_posts() ) : $r->the_post(); ?>
 			<li>
-				<a href="<?php the_permalink(); ?>"><?php get_the_title() ? the_title() : the_ID(); ?></a>
+				<a href="<?php the_permalink(); ?>"><?php echo get_the_title() ? get_the_title() : __('(no title)'); ?></a>
 			<?php if ( $show_date ) : ?>
 				<span class="post-date"><?php echo get_the_date(); ?></span>
 			<?php endif; ?>