diff --git a/demo/Actions/Greet.php b/demo/Actions/Greet.php
index 504e66e..e877f87 100644
--- a/demo/Actions/Greet.php
+++ b/demo/Actions/Greet.php
@@ -14,12 +14,12 @@
 namespace Chevere\Demo\Actions;
 
 use Chevere\Action\Action;
-use Chevere\Parameter\Interfaces\ParameterInterface;
+use Chevere\Parameter\Interfaces\StringParameterInterface;
 use function Chevere\Parameter\string;
 
 class Greet extends Action
 {
-    public static function return(): ParameterInterface
+    public static function return(): StringParameterInterface
     {
         return string('/^Hello, /');
     }
diff --git a/demo/Actions/ImageResize.php b/demo/Actions/ImageResize.php
index c58e9fb..22cd513 100644
--- a/demo/Actions/ImageResize.php
+++ b/demo/Actions/ImageResize.php
@@ -14,12 +14,12 @@
 namespace Chevere\Demo\Actions;
 
 use Chevere\Action\Action;
-use Chevere\Parameter\Interfaces\ParameterInterface;
+use Chevere\Parameter\Interfaces\StringParameterInterface;
 use function Chevere\Parameter\string;
 
 class ImageResize extends Action
 {
-    public static function return(): ParameterInterface
+    public static function return(): StringParameterInterface
     {
         return string();
     }
diff --git a/demo/Actions/StoreFile.php b/demo/Actions/StoreFile.php
index 7572d3d..44a88e9 100644
--- a/demo/Actions/StoreFile.php
+++ b/demo/Actions/StoreFile.php
@@ -14,12 +14,12 @@
 namespace Chevere\Demo\Actions;
 
 use Chevere\Action\Action;
-use Chevere\Parameter\Interfaces\ParameterInterface;
+use Chevere\Parameter\Interfaces\NullParameterInterface;
 use function Chevere\Parameter\null;
 
 class StoreFile extends Action
 {
-    public static function return(): ParameterInterface
+    public static function return(): NullParameterInterface
     {
         return null();
     }