diff --git a/lib/portfinder.js b/lib/portfinder.js
index 89c1d6b..8102c42 100644
--- a/lib/portfinder.js
+++ b/lib/portfinder.js
@@ -27,9 +27,9 @@ internals.testPort = function(options, callback) {
     options = {};
   }
 
-  options.port   = options.port   || exports.basePort;
-  options.host   = options.host   || null;
-  options.server = options.server || net.createServer(function () {
+  options.port   = +options.port   || exports.basePort;
+  options.host   = options.host    || null;
+  options.server = options.server  || net.createServer(function () {
     //
     // Create an empty listener for the port testing server.
     //