diff --git a/imageapi.module b/imageapi.module
index c86c0bf..12e36bf 100644
--- a/imageapi.module
+++ b/imageapi.module
@@ -162,6 +162,7 @@ function imageapi_toolkit_invoke($method, &$image, array $params = array()) {
   if (function_exists($function)) {
     array_unshift($params, $image);
     $params[0] = &$image;
+    $params[1] = &$params[1];
     return call_user_func_array($function, $params);
   }
   watchdog('imageapi', 'The selected image handling toolkit %toolkit can not correctly process %function.', array('%toolkit' => $image->toolkit, '%function' => $function), WATCHDOG_ERROR);