diff --git a/lib/pool.js b/lib/pool.js
index 428681c..ebc2db6 100644
--- a/lib/pool.js
+++ b/lib/pool.js
@@ -77,7 +77,7 @@ var pool = module.exports = function pool(options, authorizeFn){
 
     function SetupVarDiff(){
         Object.keys(options.ports).forEach(function(port) {
-            _this.setVarDiff(port, new varDiff(port, options.ports[port]));    
+            _this.setVarDiff(port, new varDiff(port, options.ports[port].varDiff));
         });
     }