diff --git a/wsclient.inc b/wsclient.inc
index 4040b06..9c4e980 100644
--- a/wsclient.inc
+++ b/wsclient.inc
@@ -52,7 +52,7 @@ class WSClientServiceDescription extends Entity {
       // Assign named arguments and hidden parameters.
       foreach ($this->operations[$operation]['parameter'] as $param => $info) {
         if (isset($arguments[$param])) {
-          $named_arguments[$param] = $arguments[$param];
+          $named_arguments[$param] = $info['default value'];
           unset($arguments[$param]);
           unset($remaining_params[$param]);
         }