Index: wp-includes/locale.php
===================================================================
--- wp-includes/locale.php	(revision 19726)
+++ wp-includes/locale.php	(working copy)
@@ -333,7 +333,8 @@
 	 * @return bool Whether locale is RTL.
 	 */
 	 function is_rtl() {
-	 	return 'rtl' == $this->text_direction;
+		$rtl_locales = array( 'ar', 'ckb', 'fa_IR', 'he_IL', 'ug_CN' );
+	 	return in_array( get_locale(), $rtl_locales ) || 'rtl' == $this->text_direction;
 	 }
 }