diff --git a/lib/Thumbor/Url/Builder.php b/lib/Thumbor/Url/Builder.php
index f61013c..9127e30 100644
--- a/lib/Thumbor/Url/Builder.php
+++ b/lib/Thumbor/Url/Builder.php
@@ -55,6 +55,11 @@ public function __construct($server, $secret, $original)
         $this->commands = new CommandSet();
     }
 
+    public function __clone()
+    {
+        $this->commands = clone $this->commands;
+    }
+
     // Proxy remaining method calls to CommandSet
     public function __call($method, $args)
     {