Index: wp-includes/functions.php
===================================================================
--- wp-includes/functions.php	(revision 11557)
+++ wp-includes/functions.php	(working copy)
@@ -2682,7 +2682,7 @@
 		} else {
 			$wp_smiliessearch .= '|';
 		}
-		$wp_smiliessearch .= preg_quote($rest);
+		$wp_smiliessearch .= preg_quote($rest, '/');
 	}
 
 	$wp_smiliessearch .= ')(?:\s|$)/m';