diff --git a/src/router/BaseRouter.php b/src/router/BaseRouter.php
index 650bab8..ea8e955 100644
--- a/src/router/BaseRouter.php
+++ b/src/router/BaseRouter.php
@@ -15,7 +15,7 @@
 
 abstract class BaseRouter<+TResponder> {
   abstract protected function getRoutes(
-  ): ImmMap<HttpMethod, ImmMap<string, TResponder>>;
+  ): KeyedContainer<HttpMethod, KeyedContainer<string, TResponder>>;
 
   final public function routeMethodAndPath(
     HttpMethod $method,