diff --git a/lib/Cake/Utility/CakeTime.php b/lib/Cake/Utility/CakeTime.php
index af2a06a6f..465b6d1b7 100644
--- a/lib/Cake/Utility/CakeTime.php
+++ b/lib/Cake/Utility/CakeTime.php
@@ -1138,7 +1138,7 @@ class CakeTime {
 			if (function_exists('mb_check_encoding')) {
 				$valid = mb_check_encoding($format, $encoding);
 			} else {
-				$valid = !Multibyte::checkMultibyte($format);
+				$valid = Multibyte::checkMultibyte($format);
 			}
 			if (!$valid) {
 				$format = utf8_encode($format);