diff --git a/lib/http.js b/lib/http.js
index c18a8683df9..1a1e6d75457 100644
--- a/lib/http.js
+++ b/lib/http.js
@@ -1437,12 +1437,12 @@ function getAgent(options) {
 
   var _opts = {};
 
-  if (options instanceof String) {
+  if (typeof options === 'string') {
     port = arguments[1] || 80;
     id = options + ':' + port;
     _opts.host = options;
     _opts.port = port;
-  } else if (options instanceof Object) {
+  } else if (options && options === 'object') {
     if (options.port || options.host) {
       host = options.host || 'localhost';
       port = options.port || 80;