diff --git a/testing/mochitest/dynamic/getMyDirectory.sjs b/testing/mochitest/dynamic/getMyDirectory.sjs
index c154fe0b03c9..1bf6d660b037 100644
--- a/testing/mochitest/dynamic/getMyDirectory.sjs
+++ b/testing/mochitest/dynamic/getMyDirectory.sjs
@@ -3,7 +3,7 @@ function handleRequest(request, response)
   var file;
   getObjectState("SERVER_ROOT", function(serverRoot)
   {
-    var ref = request.getHeader("Referer");
+    var ref = request.getHeader("Referer").split("?")[0];
     // 8 is "https://".length which is the longest string before the host.
     var pathStart = ref.indexOf("/", 8) + 1;
     var pathEnd = ref.lastIndexOf("/") + 1;