diff --git a/system/Router/Router.php b/system/Router/Router.php
index 2bb050de30ae..0cd1614991ee 100644
--- a/system/Router/Router.php
+++ b/system/Router/Router.php
@@ -247,7 +247,7 @@ public function getFilters(): array
      */
     public function controllerName()
     {
-        return $this->translateURIDashes
+        return $this->translateURIDashes && ! $this->controller instanceof Closure
             ? str_replace('-', '_', $this->controller)
             : $this->controller;
     }
diff --git a/tests/system/Router/RouterTest.php b/tests/system/Router/RouterTest.php
index bb5302e721dc..5d51bf2fd38c 100644
--- a/tests/system/Router/RouterTest.php
+++ b/tests/system/Router/RouterTest.php
@@ -13,6 +13,7 @@
 
 namespace CodeIgniter\Router;
 
+use Closure;
 use CodeIgniter\Config\Factories;
 use CodeIgniter\Config\Services;
 use CodeIgniter\Exceptions\PageNotFoundException;
@@ -69,6 +70,7 @@ private function createRouteCollection(?Routing $routingConfig = null): void
             'posts/(:num)/edit'                               => 'Blog::edit/$1',
             'books/(:num)/(:alpha)/(:num)'                    => 'Blog::show/$3/$1',
             'closure/(:num)/(:alpha)'                         => static fn ($num, $str) => $num . '-' . $str,
+            'closure-dash/(:num)/(:alpha)'                    => static fn ($num, $str) => $num . '-' . $str,
             '{locale}/pages'                                  => 'App\Pages::list_all',
             'test/(:any)/lang/{locale}'                       => 'App\Pages::list_all',
             'admin/admins'                                    => 'App\Admin\Admins::list_all',
@@ -216,6 +218,22 @@ public function testClosures(): void
         $this->assertSame($expects, '123-alpha');
     }
 
+    public function testClosuresWithTranslateURIDashes(): void
+    {
+        $router = new Router($this->collection, $this->request);
+        $router->setTranslateURIDashes(true);
+
+        $router->handle('closure-dash/123/alpha');
+        $closure = $router->controllerName();
+
+        $this->assertInstanceOf(Closure::class, $closure);
+
+        $expects = $closure(...$router->params());
+
+        $this->assertIsCallable($router->controllerName());
+        $this->assertSame($expects, '123-alpha');
+    }
+
     public function testAutoRouteFindsDefaultControllerAndMethod(): void
     {
         $this->collection->setAutoRoute(true);
diff --git a/user_guide_src/source/changelogs/v4.5.6.rst b/user_guide_src/source/changelogs/v4.5.6.rst
index 44b11b724cb9..2ea1f1ce46b7 100644
--- a/user_guide_src/source/changelogs/v4.5.6.rst
+++ b/user_guide_src/source/changelogs/v4.5.6.rst
@@ -36,6 +36,8 @@ Bugs Fixed
 
 - **Parser:** Fixed bug that caused equal key names to be replaced by the key name defined first.
 
+- **Routing:** Fixed a TypeError in `str_replace()` when `Routing::$translateURIDashes` is set to `true` and a route is defined using a closure.
+
 See the repo's
 `CHANGELOG.md <https://github.com/codeigniter4/CodeIgniter4/blob/develop/CHANGELOG.md>`_
 for a complete list of bugs fixed.