diff --git a/wp-includes/classes.php b/wp-includes/classes.php
index 40a41c0215..47470d3048 100644
--- a/wp-includes/classes.php
+++ b/wp-includes/classes.php
@@ -224,6 +224,8 @@ class WP {
 		foreach (array_keys($this->query_vars) as $wpvar) {
 			if ( '' != $this->query_vars[$wpvar] ) {
 				$this->query_string .= (strlen($this->query_string) < 1) ? '' : '&';
+				if ( !is_scalar($this->query_vars[$wpvar]) ) // Discard non-scalars.
+					continue;
 				$this->query_string .= $wpvar . '=' . rawurlencode($this->query_vars[$wpvar]);
 			}
 		}