diff --git a/system/Router/AutoRouter.php b/system/Router/AutoRouter.php
index f7cd02a3d329..c35e375cfa2f 100644
--- a/system/Router/AutoRouter.php
+++ b/system/Router/AutoRouter.php
@@ -157,10 +157,13 @@ public function getRoute(string $uri, string $httpVerb): array
 
         // Load the file so that it's available for CodeIgniter.
         $file = APPPATH . 'Controllers/' . $this->directory . $controllerName . '.php';
-        if (is_file($file)) {
-            include_once $file;
+
+        if (! is_file($file)) {
+            throw PageNotFoundException::forControllerNotFound($this->controller, $this->method);
         }
 
+        include_once $file;
+
         // Ensure the controller stores the fully-qualified class name
         // We have to check for a length over 1, since by default it will be '\'
         if (strpos($this->controller, '\\') === false && strlen($this->defaultNamespace) > 1) {
diff --git a/tests/_support/_controller/Admin_user.php b/tests/_support/_controller/Admin_user.php
new file mode 100644
index 000000000000..62e154410955
--- /dev/null
+++ b/tests/_support/_controller/Admin_user.php
@@ -0,0 +1,21 @@
+<?php
+
+/**
+ * This file is part of CodeIgniter 4 framework.
+ *
+ * (c) CodeIgniter Foundation <admin@codeigniter.com>
+ *
+ * For the full copyright and license information, please view
+ * the LICENSE file that was distributed with this source code.
+ */
+
+namespace App\Controllers;
+
+use CodeIgniter\Controller;
+
+class Admin_user extends Controller
+{
+    public function show_list(): void
+    {
+    }
+}
diff --git a/tests/_support/_controller/Dash_folder/Dash_controller.php b/tests/_support/_controller/Dash_folder/Dash_controller.php
new file mode 100644
index 000000000000..c474aff32e6e
--- /dev/null
+++ b/tests/_support/_controller/Dash_folder/Dash_controller.php
@@ -0,0 +1,25 @@
+<?php
+
+/**
+ * This file is part of CodeIgniter 4 framework.
+ *
+ * (c) CodeIgniter Foundation <admin@codeigniter.com>
+ *
+ * For the full copyright and license information, please view
+ * the LICENSE file that was distributed with this source code.
+ */
+
+namespace App\Controllers\Dash_folder;
+
+use CodeIgniter\Controller;
+
+class Dash_controller extends Controller
+{
+    public function getSomemethod(): void
+    {
+    }
+
+    public function getDash_method(): void
+    {
+    }
+}
diff --git a/tests/_support/_controller/Dash_folder/Home.php b/tests/_support/_controller/Dash_folder/Home.php
new file mode 100644
index 000000000000..20b28e109721
--- /dev/null
+++ b/tests/_support/_controller/Dash_folder/Home.php
@@ -0,0 +1,21 @@
+<?php
+
+/**
+ * This file is part of CodeIgniter 4 framework.
+ *
+ * (c) CodeIgniter Foundation <admin@codeigniter.com>
+ *
+ * For the full copyright and license information, please view
+ * the LICENSE file that was distributed with this source code.
+ */
+
+namespace App\Controllers\Dash_folder;
+
+use CodeIgniter\Controller;
+
+class Home extends Controller
+{
+    public function getIndex(): void
+    {
+    }
+}
diff --git a/tests/_support/_controller/Dash_folder/Mycontroller.php b/tests/_support/_controller/Dash_folder/Mycontroller.php
new file mode 100644
index 000000000000..2aef903bc891
--- /dev/null
+++ b/tests/_support/_controller/Dash_folder/Mycontroller.php
@@ -0,0 +1,21 @@
+<?php
+
+/**
+ * This file is part of CodeIgniter 4 framework.
+ *
+ * (c) CodeIgniter Foundation <admin@codeigniter.com>
+ *
+ * For the full copyright and license information, please view
+ * the LICENSE file that was distributed with this source code.
+ */
+
+namespace App\Controllers\Dash_folder;
+
+use CodeIgniter\Controller;
+
+class Mycontroller extends Controller
+{
+    public function getSomemethod(): void
+    {
+    }
+}
diff --git a/tests/_support/_controller/Mycontroller.php b/tests/_support/_controller/Mycontroller.php
new file mode 100644
index 000000000000..d107198c78d4
--- /dev/null
+++ b/tests/_support/_controller/Mycontroller.php
@@ -0,0 +1,25 @@
+<?php
+
+/**
+ * This file is part of CodeIgniter 4 framework.
+ *
+ * (c) CodeIgniter Foundation <admin@codeigniter.com>
+ *
+ * For the full copyright and license information, please view
+ * the LICENSE file that was distributed with this source code.
+ */
+
+namespace App\Controllers;
+
+use CodeIgniter\Controller;
+
+class Mycontroller extends Controller
+{
+    public function getIndex(): void
+    {
+    }
+
+    public function getSomemethod($first = ''): void
+    {
+    }
+}
diff --git a/tests/_support/_controller/Product.php b/tests/_support/_controller/Product.php
new file mode 100644
index 000000000000..88951b8d90c1
--- /dev/null
+++ b/tests/_support/_controller/Product.php
@@ -0,0 +1,21 @@
+<?php
+
+/**
+ * This file is part of CodeIgniter 4 framework.
+ *
+ * (c) CodeIgniter Foundation <admin@codeigniter.com>
+ *
+ * For the full copyright and license information, please view
+ * the LICENSE file that was distributed with this source code.
+ */
+
+namespace App\Controllers;
+
+use CodeIgniter\Controller;
+
+class Product extends Controller
+{
+    public function index(): void
+    {
+    }
+}
diff --git a/tests/_support/_controller/Subfolder/Mycontroller.php b/tests/_support/_controller/Subfolder/Mycontroller.php
new file mode 100644
index 000000000000..1da9d80843b3
--- /dev/null
+++ b/tests/_support/_controller/Subfolder/Mycontroller.php
@@ -0,0 +1,21 @@
+<?php
+
+/**
+ * This file is part of CodeIgniter 4 framework.
+ *
+ * (c) CodeIgniter Foundation <admin@codeigniter.com>
+ *
+ * For the full copyright and license information, please view
+ * the LICENSE file that was distributed with this source code.
+ */
+
+namespace App\Controllers\Subfolder;
+
+use CodeIgniter\Controller;
+
+class Mycontroller extends Controller
+{
+    public function getSomemethod(): void
+    {
+    }
+}
diff --git a/tests/_support/_controller/foo/bar/baz/Some_controller.php b/tests/_support/_controller/foo/bar/baz/Some_controller.php
new file mode 100644
index 000000000000..25fe509c56cc
--- /dev/null
+++ b/tests/_support/_controller/foo/bar/baz/Some_controller.php
@@ -0,0 +1,21 @@
+<?php
+
+/**
+ * This file is part of CodeIgniter 4 framework.
+ *
+ * (c) CodeIgniter Foundation <admin@codeigniter.com>
+ *
+ * For the full copyright and license information, please view
+ * the LICENSE file that was distributed with this source code.
+ */
+
+namespace App\Controllers\foo\bar\baz;
+
+use CodeIgniter\Controller;
+
+class Some_controller extends Controller
+{
+    public function some_method($first = ''): void
+    {
+    }
+}
diff --git "a/tests/_support/_controller/\316\246.php" "b/tests/_support/_controller/\316\246.php"
new file mode 100644
index 000000000000..a48ba76f77cd
--- /dev/null
+++ "b/tests/_support/_controller/\316\246.php"
@@ -0,0 +1,21 @@
+<?php
+
+/**
+ * This file is part of CodeIgniter 4 framework.
+ *
+ * (c) CodeIgniter Foundation <admin@codeigniter.com>
+ *
+ * For the full copyright and license information, please view
+ * the LICENSE file that was distributed with this source code.
+ */
+
+namespace App\Controllers;
+
+use CodeIgniter\Controller;
+
+class Φ extends Controller
+{
+    public function getIndex(): void
+    {
+    }
+}
diff --git "a/tests/_support/_controller/\316\246/Home.php" "b/tests/_support/_controller/\316\246/Home.php"
new file mode 100644
index 000000000000..3ee7e7aea271
--- /dev/null
+++ "b/tests/_support/_controller/\316\246/Home.php"
@@ -0,0 +1,21 @@
+<?php
+
+/**
+ * This file is part of CodeIgniter 4 framework.
+ *
+ * (c) CodeIgniter Foundation <admin@codeigniter.com>
+ *
+ * For the full copyright and license information, please view
+ * the LICENSE file that was distributed with this source code.
+ */
+
+namespace App\Controllers\Φ;
+
+use CodeIgniter\Controller;
+
+class Home extends Controller
+{
+    public function getIndex(): void
+    {
+    }
+}
diff --git a/tests/system/CodeIgniterTest.php b/tests/system/CodeIgniterTest.php
index b7b5e092e609..505d1f5e5a7b 100644
--- a/tests/system/CodeIgniterTest.php
+++ b/tests/system/CodeIgniterTest.php
@@ -13,6 +13,7 @@
 
 use CodeIgniter\Config\Services;
 use CodeIgniter\Exceptions\ConfigException;
+use CodeIgniter\Exceptions\PageNotFoundException;
 use CodeIgniter\HTTP\Response;
 use CodeIgniter\Router\Exceptions\RedirectException;
 use CodeIgniter\Router\RouteCollection;
@@ -25,6 +26,7 @@
 use Config\Modules;
 use Config\Routing;
 use Tests\Support\Filters\Customfilter;
+use Tests\Support\Filters\RedirectFilter;
 
 /**
  * @runTestsInSeparateProcesses
@@ -926,4 +928,30 @@ public static function providePageCacheWithCacheQueryString(): iterable
             '$cacheQueryString=array' => [['important_parameter'], 3, $testingUrls],
         ];
     }
+
+    /**
+     * See https://github.com/codeigniter4/CodeIgniter4/issues/7205
+     */
+    public function testRunControllerNotFoundBeforeFilter(): void
+    {
+        $_SERVER['argv'] = ['index.php'];
+        $_SERVER['argc'] = 1;
+
+        $_SERVER['REQUEST_URI'] = '/cannotFound';
+        $_SERVER['SCRIPT_NAME'] = '/index.php';
+
+        // Inject mock router.
+        $routes = Services::routes();
+        $routes->setAutoRoute(true);
+
+        // Inject the before filter.
+        $filterConfig                            = config('Filters');
+        $filterConfig->aliases['redirectFilter'] = RedirectFilter::class;
+        $filterConfig->globals['before']         = ['redirectFilter'];
+        Services::filters($filterConfig);
+
+        $this->expectException(PageNotFoundException::class);
+
+        $this->codeigniter->run($routes);
+    }
 }
diff --git a/tests/system/Router/RouteCollectionTest.php b/tests/system/Router/RouteCollectionTest.php
index d6b7e0dfe6ac..985326dcf66d 100644
--- a/tests/system/Router/RouteCollectionTest.php
+++ b/tests/system/Router/RouteCollectionTest.php
@@ -11,6 +11,7 @@
 
 namespace CodeIgniter\Router;
 
+use App\Controllers\Product;
 use CodeIgniter\Config\Services;
 use CodeIgniter\controller;
 use CodeIgniter\Exceptions\PageNotFoundException;
@@ -1778,10 +1779,14 @@ public function testAutoRoutesControllerNameReturnsFQCN($namespace): void
         $routes->setAutoRoute(true);
         $routes->setDefaultNamespace($namespace);
 
+        copy(TESTPATH . '_support/_controller/Product.php', APPPATH . 'Controllers/Product.php');
+
         $router = new Router($routes, Services::request());
         $router->handle('/product');
 
-        $this->assertSame('\App\\Controllers\\Product', $router->controllerName());
+        unlink(APPPATH . 'Controllers/Product.php');
+
+        $this->assertSame('\\' . Product::class, $router->controllerName());
     }
 
     /**
@@ -1797,10 +1802,14 @@ public function testRoutesControllerNameReturnsFQCN($namespace): void
         $routes->setDefaultNamespace($namespace);
         $routes->get('/product', 'Product');
 
+        copy(TESTPATH . '_support/_controller/Product.php', APPPATH . 'Controllers/Product.php');
+
         $router = new Router($routes, Services::request());
         $router->handle('/product');
 
-        $this->assertSame('\App\\Controllers\\Product', $router->controllerName());
+        unlink(APPPATH . 'Controllers/Product.php');
+
+        $this->assertSame('\\' . Product::class, $router->controllerName());
     }
 
     public function testRoutePriorityDetected(): void
diff --git a/tests/system/Router/RouterTest.php b/tests/system/Router/RouterTest.php
index d0c9b5a664ab..60dd669172e5 100644
--- a/tests/system/Router/RouterTest.php
+++ b/tests/system/Router/RouterTest.php
@@ -197,14 +197,18 @@ public function testClosures(): void
     public function testAutoRouteFindsDefaultControllerAndMethod(): void
     {
         $this->collection->setAutoRoute(true);
-        $this->collection->setDefaultController('Test');
-        $this->collection->setDefaultMethod('test');
+        $this->collection->setDefaultController('Mycontroller');
+        $this->collection->setDefaultMethod('getSomemethod');
         $router = new Router($this->collection, $this->request);
 
+        copy(TESTPATH . '_support/_controller/Mycontroller.php', APPPATH . 'Controllers/Mycontroller.php');
+
         $router->autoRoute('/');
 
-        $this->assertSame('Test', $router->controllerName());
-        $this->assertSame('test', $router->methodName());
+        unlink(APPPATH . 'Controllers/Mycontroller.php');
+
+        $this->assertSame('Mycontroller', $router->controllerName());
+        $this->assertSame('getSomemethod', $router->methodName());
     }
 
     public function testAutoRouteFindsControllerWithFileAndMethod(): void
@@ -212,10 +216,14 @@ public function testAutoRouteFindsControllerWithFileAndMethod(): void
         $this->collection->setAutoRoute(true);
         $router = new Router($this->collection, $this->request);
 
-        $router->autoRoute('myController/someMethod');
+        copy(TESTPATH . '_support/_controller/Mycontroller.php', APPPATH . 'Controllers/Mycontroller.php');
+
+        $router->autoRoute('mycontroller/getSomemethod');
+
+        unlink(APPPATH . 'Controllers/Mycontroller.php');
 
-        $this->assertSame('MyController', $router->controllerName());
-        $this->assertSame('someMethod', $router->methodName());
+        $this->assertSame('Mycontroller', $router->controllerName());
+        $this->assertSame('getSomemethod', $router->methodName());
     }
 
     public function testAutoRouteFindsControllerWithFile(): void
@@ -223,9 +231,13 @@ public function testAutoRouteFindsControllerWithFile(): void
         $this->collection->setAutoRoute(true);
         $router = new Router($this->collection, $this->request);
 
-        $router->autoRoute('myController');
+        copy(TESTPATH . '_support/_controller/Mycontroller.php', APPPATH . 'Controllers/Mycontroller.php');
+
+        $router->autoRoute('mycontroller');
+
+        unlink(APPPATH . 'Controllers/Mycontroller.php');
 
-        $this->assertSame('MyController', $router->controllerName());
+        $this->assertSame('Mycontroller', $router->controllerName());
         $this->assertSame('index', $router->methodName());
     }
 
@@ -236,12 +248,16 @@ public function testAutoRouteFindsControllerWithSubfolder(): void
 
         mkdir(APPPATH . 'Controllers/Subfolder');
 
-        $router->autoRoute('subfolder/myController/someMethod');
+        copy(TESTPATH . '_support/_controller/Subfolder/Mycontroller.php', APPPATH . 'Controllers/Subfolder/Mycontroller.php');
+
+        $router->autoRoute('subfolder/mycontroller/getSomemethod');
+
+        unlink(APPPATH . 'Controllers/Subfolder/Mycontroller.php');
 
         rmdir(APPPATH . 'Controllers/Subfolder');
 
-        $this->assertSame('MyController', $router->controllerName());
-        $this->assertSame('someMethod', $router->methodName());
+        $this->assertSame('Mycontroller', $router->controllerName());
+        $this->assertSame('getSomemethod', $router->methodName());
     }
 
     public function testAutoRouteFindsDashedSubfolder(): void
@@ -251,9 +267,11 @@ public function testAutoRouteFindsDashedSubfolder(): void
         $router->setTranslateURIDashes(true);
 
         mkdir(APPPATH . 'Controllers/Dash_folder');
+        copy(TESTPATH . '_support/_controller/Dash_folder/Mycontroller.php', APPPATH . 'Controllers/Dash_folder/Mycontroller.php');
 
         $router->autoRoute('dash-folder/mycontroller/somemethod');
 
+        unlink(APPPATH . 'Controllers/Dash_folder/Mycontroller.php');
         rmdir(APPPATH . 'Controllers/Dash_folder');
 
         $this->assertSame('Dash_folder/', $router->directory());
@@ -268,16 +286,16 @@ public function testAutoRouteFindsDashedController(): void
         $router->setTranslateURIDashes(true);
 
         mkdir(APPPATH . 'Controllers/Dash_folder');
-        file_put_contents(APPPATH . 'Controllers/Dash_folder/Dash_controller.php', '');
+        copy(TESTPATH . '_support/_controller/Dash_folder/Dash_controller.php', APPPATH . 'Controllers/Dash_folder/Dash_controller.php');
 
-        $router->autoRoute('dash-folder/dash-controller/somemethod');
+        $router->autoRoute('dash-folder/dash-controller/getSomemethod');
 
         unlink(APPPATH . 'Controllers/Dash_folder/Dash_controller.php');
         rmdir(APPPATH . 'Controllers/Dash_folder');
 
         $this->assertSame('Dash_folder/', $router->directory());
         $this->assertSame('Dash_controller', $router->controllerName());
-        $this->assertSame('somemethod', $router->methodName());
+        $this->assertSame('getSomemethod', $router->methodName());
     }
 
     public function testAutoRouteFindsDashedMethod(): void
@@ -287,16 +305,16 @@ public function testAutoRouteFindsDashedMethod(): void
         $router->setTranslateURIDashes(true);
 
         mkdir(APPPATH . 'Controllers/Dash_folder');
-        file_put_contents(APPPATH . 'Controllers/Dash_folder/Dash_controller.php', '');
+        copy(TESTPATH . '_support/_controller/Dash_folder/Dash_controller.php', APPPATH . 'Controllers/Dash_folder/Dash_controller.php');
 
-        $router->autoRoute('dash-folder/dash-controller/dash-method');
+        $router->autoRoute('dash-folder/dash-controller/getDash_method');
 
         unlink(APPPATH . 'Controllers/Dash_folder/Dash_controller.php');
         rmdir(APPPATH . 'Controllers/Dash_folder');
 
         $this->assertSame('Dash_folder/', $router->directory());
         $this->assertSame('Dash_controller', $router->controllerName());
-        $this->assertSame('dash_method', $router->methodName());
+        $this->assertSame('getDash_method', $router->methodName());
     }
 
     public function testAutoRouteFindsDefaultDashFolder(): void
@@ -306,9 +324,11 @@ public function testAutoRouteFindsDefaultDashFolder(): void
         $router->setTranslateURIDashes(true);
 
         mkdir(APPPATH . 'Controllers/Dash_folder');
+        copy(TESTPATH . '_support/_controller/Dash_folder/Home.php', APPPATH . 'Controllers/Dash_folder/Home.php');
 
         $router->autoRoute('dash-folder');
 
+        unlink(APPPATH . 'Controllers/Dash_folder/Home.php');
         rmdir(APPPATH . 'Controllers/Dash_folder');
 
         $this->assertSame('Dash_folder/', $router->directory());
@@ -323,9 +343,11 @@ public function testAutoRouteFindsMByteDir(): void
         $router->setTranslateURIDashes(true);
 
         mkdir(APPPATH . 'Controllers/Φ');
+        copy(TESTPATH . '_support/_controller/Φ/Home.php', APPPATH . 'Controllers/Φ/Home.php');
 
         $router->autoRoute('Φ');
 
+        unlink(APPPATH . 'Controllers/Φ/Home.php');
         rmdir(APPPATH . 'Controllers/Φ');
 
         $this->assertSame('Φ/', $router->directory());
@@ -339,11 +361,11 @@ public function testAutoRouteFindsMByteController(): void
         $router = new Router($this->collection, $this->request);
         $router->setTranslateURIDashes(true);
 
-        file_put_contents(APPPATH . 'Controllers/Φ', '');
+        copy(TESTPATH . '_support/_controller/Φ.php', APPPATH . 'Controllers/Φ.php');
 
         $router->autoRoute('Φ');
 
-        unlink(APPPATH . 'Controllers/Φ');
+        unlink(APPPATH . 'Controllers/Φ.php');
 
         $this->assertSame('Φ', $router->controllerName());
         $this->assertSame('index', $router->methodName());
@@ -732,7 +754,11 @@ public function testTranslateURIDashesForAutoRoute(): void
         $router = new Router($this->collection, $this->request);
         $router->setTranslateURIDashes(true);
 
-        $router->autoRoute('admin-user/show-list');
+        copy(TESTPATH . '_support/_controller/Admin_user.php', APPPATH . 'Controllers/Admin_user.php');
+
+        $router->autoRoute('admin_user/show_list');
+
+        unlink(APPPATH . 'Controllers/Admin_user.php');
 
         $this->assertSame('Admin_user', $router->controllerName());
         $this->assertSame('show_list', $router->methodName());
@@ -746,10 +772,14 @@ public function testAutoRouteMatchesZeroParams(): void
         $this->collection->setAutoRoute(true);
         $router = new Router($this->collection, $this->request);
 
-        $router->autoRoute('myController/someMethod/0/abc');
+        copy(TESTPATH . '_support/_controller/Mycontroller.php', APPPATH . 'Controllers/Mycontroller.php');
 
-        $this->assertSame('MyController', $router->controllerName());
-        $this->assertSame('someMethod', $router->methodName());
+        $router->autoRoute('mycontroller/getSomemethod/0/abc');
+
+        $this->assertSame('Mycontroller', $router->controllerName());
+        $this->assertSame('getSomemethod', $router->methodName());
+
+        unlink(APPPATH . 'Controllers/Mycontroller.php');
 
         $expected = [
             '0',
@@ -817,9 +847,19 @@ public function testRouterPriorDirectory(): void
         $this->collection->setAutoRoute(true);
         $router = new Router($this->collection, $this->request);
 
+        mkdir(APPPATH . 'Controllers/foo');
+        mkdir(APPPATH . 'Controllers/foo/bar');
+        mkdir(APPPATH . 'Controllers/foo/bar/baz');
+        copy(TESTPATH . '_support/_controller/foo/bar/baz/Some_controller.php', APPPATH . 'Controllers/foo/bar/baz/Some_controller.php');
+
         $router->setDirectory('foo/bar/baz', false, true);
         $router->handle('Some_controller/some_method/param1/param2/param3');
 
+        unlink(APPPATH . 'Controllers/foo/bar/baz/Some_controller.php');
+        rmdir(APPPATH . 'Controllers/foo/bar/baz');
+        rmdir(APPPATH . 'Controllers/foo/bar');
+        rmdir(APPPATH . 'Controllers/foo');
+
         $this->assertSame('foo/bar/baz/', $router->directory());
         $this->assertSame('Some_controller', $router->controllerName());
         $this->assertSame('some_method', $router->methodName());
diff --git a/user_guide_src/source/changelogs/v4.5.0.rst b/user_guide_src/source/changelogs/v4.5.0.rst
index 2b6fc7299231..5100ded28a89 100644
--- a/user_guide_src/source/changelogs/v4.5.0.rst
+++ b/user_guide_src/source/changelogs/v4.5.0.rst
@@ -43,6 +43,8 @@ class, and even if it were extended, there is no way to replace it.
 Others
 ------
 
+- **AutoRouting Legacy:** Changed so that a ``PageNotFoundException`` is thrown
+  if the controller corresponding to the request URI does not exist.
 - **Logger:** The :php:func:`log_message()` function and the logger methods in
   ``CodeIgniter\Log\Logger`` now do not return ``bool`` values. The return types
   have been fixed to ``void`` to follow the PSR-3 interface.
diff --git a/user_guide_src/source/incoming/controllers.rst b/user_guide_src/source/incoming/controllers.rst
index 8bc9e90d581f..f53609023c52 100644
--- a/user_guide_src/source/incoming/controllers.rst
+++ b/user_guide_src/source/incoming/controllers.rst
@@ -412,6 +412,10 @@ without route definitions. The auto-routing is disabled by default.
 
 .. important:: Auto Routing (Legacy) routes a HTTP request with **any** HTTP method to a controller method.
 
+.. important:: Since v4.5.0, if Auto Routing (Legacy) doesn't find the controller,
+    it will throw ``PageNotFoundException`` exception before the Controller Filters
+    execute.
+
 Consider this URI::
 
     example.com/index.php/helloworld/
diff --git a/user_guide_src/source/installation/upgrade_450.rst b/user_guide_src/source/installation/upgrade_450.rst
index 56b1f37c011e..04607dde6489 100644
--- a/user_guide_src/source/installation/upgrade_450.rst
+++ b/user_guide_src/source/installation/upgrade_450.rst
@@ -126,6 +126,18 @@ Factories
 In the unlikely event, you have inherited the Factories, stop inheriting and
 copy the code into your Factories class.
 
+Auto Routing (Legacy)
+=====================
+
+In previous versions, the controller filters might be executed even when the
+corresponding controller was not found.
+
+This bug has been fixed and now a ``PageNotFoundException`` will be thrown and
+the filters will not be executed if the controller is not found.
+
+If you have code that depends on this bug, for example if you expect global filters
+to be executed even for non-existent pages, please add the necessary routes.
+
 Removed Deprecated Items
 ========================