Index: wp-admin/includes/dashboard.php
===================================================================
--- wp-admin/includes/dashboard.php	(revision 50343)
+++ wp-admin/includes/dashboard.php	(working copy)
@@ -1877,6 +1877,8 @@
 				<?php _e( 'Your site has critical issues that should be addressed as soon as possible to improve its performance and security.' ); ?>
 			<?php elseif ( $issues_total <= 0 ) : ?>
 				<?php _e( 'Great job! Your site currently passes all site health checks.' ); ?>
+			<?php elseif ( $issues_total == 1 ) : ?>
+				<?php _e( 'Your site&#8217;s health is looking good, but there is still one thing you can do to improve its performance and security.' ); ?>
 			<?php else : ?>
 				<?php _e( 'Your site&#8217;s health is looking good, but there are still some things you can do to improve its performance and security.' ); ?>
 			<?php endif; ?>