diff --git a/src/Symfony/Component/Routing/Generator/UrlGenerator.php b/src/Symfony/Component/Routing/Generator/UrlGenerator.php
index f0e2a48518..b1be194ba8 100644
--- a/src/Symfony/Component/Routing/Generator/UrlGenerator.php
+++ b/src/Symfony/Component/Routing/Generator/UrlGenerator.php
@@ -146,7 +146,7 @@ class UrlGenerator implements UrlGeneratorInterface
 
         // add a query string if needed
         $extra = array_diff_key($originParameters, $variables, $defaults);
-        if ($extra && $query = http_build_query($extra)) {
+        if ($extra && $query = http_build_query($extra, '', '&')) {
             $url .= '?'.$query;
         }