diff --git a/wp-includes/classes.php b/wp-includes/classes.php
index e8563ec332..a57eaa7c63 100644
--- a/wp-includes/classes.php
+++ b/wp-includes/classes.php
@@ -148,6 +148,8 @@ class WP {
 				$this->query_vars[$wpvar] = $_GET[$wpvar];
 			elseif (!empty($perma_query_vars[$wpvar]))
 				$this->query_vars[$wpvar] = $perma_query_vars[$wpvar];
+
+			$this->query_vars[$wpvar] = (string) $this->query_vars[$wpvar];
 		}
 
 		foreach ($this->private_query_vars as $var) {