diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 439fde2..f44b0eb 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -18,5 +18,26 @@ jobs:
     secrets: inherit
 
   cs-stan:
-    uses: cakephp/.github/.github/workflows/cs-stan.yml@5.x
-    secrets: inherit
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Setup PHP
+        uses: shivammathur/setup-php@v2
+        with:
+          php-version: '8.3'
+          extensions: mbstring, intl
+          coverage: none
+          tools: composer:v2
+
+      - name: Composer install
+        run: |
+          composer install --no-progress --prefer-dist --optimize-autoloader
+
+      - name: Install PHPStan
+        run: |
+          composer require --dev phpstan/phpstan
+
+      - name: Run phpstan
+        run: |
+          vendor/bin/phpstan analyse --error-format=github --configuration=phpstan.neon
diff --git a/composer.json b/composer.json
index 6ad2f87..523a7aa 100644
--- a/composer.json
+++ b/composer.json
@@ -30,8 +30,7 @@
     },
     "require-dev": {
         "phpunit/phpunit": "^10.1.0",
-        "cakephp/cakephp-codesniffer": "^5.0",
-        "vimeo/psalm": "^5.15"
+        "cakephp/cakephp-codesniffer": "^5.0"
     },
     "autoload": {
         "psr-4": {
diff --git a/phpstan.neon b/phpstan.neon
index c538d25..59f7883 100644
--- a/phpstan.neon
+++ b/phpstan.neon
@@ -3,8 +3,6 @@ includes:
 
 parameters:
 	level: 8
-	checkMissingIterableValueType: false
-	checkGenericClassInNonGenericObjectType: false
 	treatPhpDocTypesAsCertain: false
 	paths:
 		- src/
diff --git a/src/Routing/Middleware/CachedRoutingMiddleware.php b/src/Routing/Middleware/CachedRoutingMiddleware.php
index 6a1b5a1..6a3b07c 100644
--- a/src/Routing/Middleware/CachedRoutingMiddleware.php
+++ b/src/Routing/Middleware/CachedRoutingMiddleware.php
@@ -75,9 +75,14 @@ protected function buildRouteCollection(): RouteCollection
     {
         if (Cache::enabled() && $this->cacheConfig !== null) {
             try {
-                return Cache::remember(static::ROUTE_COLLECTION_CACHE_KEY, function () {
+                $cached = Cache::remember(static::ROUTE_COLLECTION_CACHE_KEY, function () {
                     return $this->prepareRouteCollection();
                 }, $this->cacheConfig);
+                if ($cached instanceof RouteCollection) {
+                    return $cached;
+                } else {
+                    Cache::delete(static::ROUTE_COLLECTION_CACHE_KEY, $this->cacheConfig);
+                }
             } catch (InvalidArgumentException $e) {
                 throw $e;
             } catch (Exception $e) {
@@ -86,7 +91,7 @@ protected function buildRouteCollection(): RouteCollection
                     middleware or other unserializable settings in your routes. The original exception message can
                     show what type of object failed to serialize.',
                     null,
-                    $e
+                    $e,
                 );
             }
         }
diff --git a/tests/TestCase/Routing/Middleware/CachedRoutingMiddlewareTest.php b/tests/TestCase/Routing/Middleware/CachedRoutingMiddlewareTest.php
index b813832..65d0b9f 100644
--- a/tests/TestCase/Routing/Middleware/CachedRoutingMiddlewareTest.php
+++ b/tests/TestCase/Routing/Middleware/CachedRoutingMiddlewareTest.php
@@ -14,9 +14,11 @@
 namespace CakeDC\CachedRouting\Test\TestCase\Routing\Middleware;
 
 use Cake\Cache\Cache;
+use Cake\Http\Response;
 use Cake\Http\ServerRequestFactory;
 use Cake\Routing\RouteBuilder;
 use Cake\Routing\RouteCollection;
+use Cake\Routing\Router;
 use Cake\TestSuite\TestCase;
 use CakeDC\CachedRouting\Routing\Exception\FailedRouteCacheException;
 use CakeDC\CachedRouting\Routing\Middleware\CachedRoutingMiddleware;
@@ -76,4 +78,27 @@ public function testFailedRouteCache(): void
         $this->expectExceptionMessage('Unable to cache route collection.');
         $middleware->process($request, new TestRequestHandler());
     }
+
+    /**
+     * Test that when cache returns a non-RouteCollection value, it gets deleted and a new RouteCollection is created.
+     */
+    public function testInvalidCachedValue(): void
+    {
+        $cacheConfigName = '_cake_router_';
+        Cache::setConfig($cacheConfigName, [
+            'engine' => 'File',
+            'path' => CACHE,
+        ]);
+
+        Cache::write(CachedRoutingMiddleware::ROUTE_COLLECTION_CACHE_KEY, 'not a route collection', $cacheConfigName);
+        $this->assertEquals('not a route collection', Cache::read(CachedRoutingMiddleware::ROUTE_COLLECTION_CACHE_KEY, $cacheConfigName));
+
+        $request = ServerRequestFactory::fromGlobals(['REQUEST_URI' => '/articles']);
+        $middleware = new CachedRoutingMiddleware(new Application(), $cacheConfigName);
+        $response = $middleware->process($request, new TestRequestHandler());
+
+        $this->assertInstanceOf(Response::class, $response);
+        $this->assertNull(Cache::read(CachedRoutingMiddleware::ROUTE_COLLECTION_CACHE_KEY, $cacheConfigName));
+        $this->assertInstanceOf(RouteCollection::class, Router::getRouteCollection());
+    }
 }