diff --git a/lib/request.js b/lib/request.js
index e87c8e9..f6c7ec7 100644
--- a/lib/request.js
+++ b/lib/request.js
@@ -248,6 +248,9 @@ function Test (app, method, path) {
 util.inherits(Test, Request);
 
 function serverAddress (app, path) {
+  if (!app) {
+    throw new Error("You must pass a valid application or server into the request");
+  }
   if ('string' === typeof app) {
     return app + path;
   }