diff --git a/DependencyInjection/DemoExtension.php b/DependencyInjection/DemoExtension.php
index c01e385..ba2f80c 100644
--- a/DependencyInjection/DemoExtension.php
+++ b/DependencyInjection/DemoExtension.php
@@ -21,7 +21,7 @@
 class DemoExtension extends AbstractPluginExtension implements PrependExtensionInterface
 {
     /**
-     * @param array<string, mixed> $configs
+     * @param array<mixed> $configs
      * @throws \Exception
      */
     public function load(array $configs, ContainerBuilder $container): void
diff --git a/Invoice/DemoSortActivityInvoiceCalculator.php b/Invoice/DemoSortActivityInvoiceCalculator.php
index 9635d2e..d890c1f 100644
--- a/Invoice/DemoSortActivityInvoiceCalculator.php
+++ b/Invoice/DemoSortActivityInvoiceCalculator.php
@@ -45,7 +45,7 @@ protected function mergeSumInvoiceItem(InvoiceItem $invoiceItem, ExportableItem
     public function getEntries(): array
     {
         $entries = $this->model->getEntries();
-        if (empty($entries)) {
+        if (\count($entries) === 0) {
             return [];
         }
 
@@ -68,7 +68,7 @@ public function getEntries(): array
             $compare_a = $a->getActivity()?->getName();
             $compare_b = $b->getActivity()?->getName();
 
-            if ($compare_a == $compare_b) {
+            if ($compare_a === $compare_b) {
                 return 0;
             }
 
diff --git a/Widget/DemoWidget.php b/Widget/DemoWidget.php
index 7628a44..dc509b5 100644
--- a/Widget/DemoWidget.php
+++ b/Widget/DemoWidget.php
@@ -17,7 +17,7 @@
 
 class DemoWidget extends AbstractWidget
 {
-    public function __construct(private UserRepository $repository)
+    public function __construct(private readonly UserRepository $repository)
     {
     }
 
@@ -41,7 +41,7 @@ public function getOptions(array $options = []): array
     }
 
     /**
-     * @param array<string, string|bool|int|null> $options
+     * @param array<string, string|bool|int|null|array<string, mixed>> $options
      */
     public function getData(array $options = []): mixed
     {
diff --git a/composer.json b/composer.json
index 8c87f8a..0da3f9a 100644
--- a/composer.json
+++ b/composer.json
@@ -54,7 +54,9 @@
         "friendsofphp/php-cs-fixer": "^3.0",
         "kimai/kimai": "dev-main",
         "phpstan/phpstan": "^2.0",
+        "phpstan/phpstan-deprecation-rules": "^2.0",
         "phpstan/phpstan-doctrine": "^2.0",
+        "phpstan/phpstan-strict-rules": "^2.0",
         "phpstan/phpstan-symfony": "^2.0",
         "symfony/console": "^6.0",
         "symfony/event-dispatcher": "^6.0"
diff --git a/phpstan.neon b/phpstan.neon
index c4993f7..9736d70 100644
--- a/phpstan.neon
+++ b/phpstan.neon
@@ -1,13 +1,17 @@
 includes:
-    - %rootDir%/../phpstan-symfony/extension.neon
-    - %rootDir%/../phpstan-symfony/rules.neon
-    - %rootDir%/../phpstan-doctrine/extension.neon
-    - %rootDir%/../phpstan-doctrine/rules.neon
-    - %rootDir%/../phpstan/conf/bleedingEdge.neon
+  - %rootDir%/../phpstan-symfony/extension.neon
+  - %rootDir%/../phpstan-symfony/rules.neon
+  - %rootDir%/../phpstan-doctrine/extension.neon
+  - %rootDir%/../phpstan-doctrine/rules.neon
+  - %rootDir%/../phpstan-deprecation-rules/rules.neon
+  - %rootDir%/../phpstan-strict-rules/rules.neon
+  - %rootDir%/../phpstan/conf/bleedingEdge.neon
 
 parameters:
-    level: 9
-    excludePaths:
-        - vendor/(?)
-    treatPhpDocTypesAsCertain: false
-    inferPrivatePropertyTypeFromConstructor: true
+  level: 9
+  excludePaths:
+    - vendor/(?)
+  treatPhpDocTypesAsCertain: false
+  inferPrivatePropertyTypeFromConstructor: true
+  doctrine:
+    allowNullablePropertyForRequiredField: true