Index: wp-includes/functions.php
===================================================================
--- wp-includes/functions.php	(revision 19998)
+++ wp-includes/functions.php	(working copy)
@@ -2357,7 +2357,7 @@
 		$wp_smiliessearch .= preg_quote($rest, '/');
 	}
 
-	$wp_smiliessearch .= ')(?:\s|$)/m';
+	$wp_smiliessearch .= ')(?=\s|$)/m';
 }
 
 /**