diff --git a/wp-includes/functions.php b/wp-includes/functions.php
index f5ac91983f..1b9ad20c24 100644
--- a/wp-includes/functions.php
+++ b/wp-includes/functions.php
@@ -404,7 +404,7 @@ function maybe_serialize($data) {
 		$data = trim($data);
 	elseif ( is_array($data) || is_object($data) )
 		return serialize($data);
-	if ( !is_serialized($data) )
+	if ( is_serialized($data) )
 		return serialize($data);
 	return $data;
 }