diff --git a/lib/router.php b/lib/router.php
index 417206e6bf..ab8c40668d 100644
--- a/lib/router.php
+++ b/lib/router.php
@@ -863,7 +863,16 @@ class Router
         if ($qpos !== false) {
             $url = substr($url, 0, $qpos+1) .
               str_replace('?', '&', substr($url, $qpos+1));
+
+            // @fixme this is a hacky workaround for http_build_query in the
+            // lower-level code and bad configs that set the default separator
+            // to & instead of &. Encoded &s in parameters will not be
+            // affected.
+            $url = substr($url, 0, $qpos+1) .
+              str_replace('&', '&', substr($url, $qpos+1));
+
         }
+
         return $url;
     }
 }