diff --git a/CHANGELOG.md b/CHANGELOG.md
index b85d5a3..d8c1035 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,11 @@
 
 All notable changes to `Slytherin` will be documented in this file.
 
+## [0.9.9](https://github.com/rougin/slytherin/compare/v0.9.7...v0.9.8) - Unreleased
+
+### Changed
+- Do not override `System` implementations if already defined from `ContainerInterface`
+
 ## [0.9.8](https://github.com/rougin/slytherin/compare/v0.9.7...v0.9.8) - 2024-05-23
 
 ### Added
diff --git a/src/Http/HttpIntegration.php b/src/Http/HttpIntegration.php
index b9c601b..623dc16 100644
--- a/src/Http/HttpIntegration.php
+++ b/src/Http/HttpIntegration.php
@@ -141,9 +141,17 @@ protected function resolve(ContainerInterface $container, ServerRequestInterface
             $request = ServerRequestFactory::fromGlobals();
         }
 
-        $container->set(System::REQUEST, $request);
+        if (! $container->has(System::REQUEST))
+        {
+            $container->set(System::REQUEST, $request);
+        }
+
+        if (! $container->has(System::RESPONSE))
+        {
+            $container->set(System::RESPONSE, $response);
+        }
 
-        return $container->set(System::RESPONSE, $response);
+        return $container;
     }
 
     /**