diff --git a/app/Http/Requests/StoreBookRequest.php b/app/Http/Requests/StoreBookRequest.php
index 9406bc6..9474c56 100644
--- a/app/Http/Requests/StoreBookRequest.php
+++ b/app/Http/Requests/StoreBookRequest.php
@@ -81,8 +81,8 @@ public function rules(): array
                 'string',
                 'filled',
                 Rule::unique('books')
-                    ->where(function ($query) {
-                        return $query->where('isbn', $this->isbn);
+                    ->where(function (\Illuminate\Database\Query\Builder $query) {
+                        $query->where('isbn', $this->isbn);
                     }),
             ],
             'publisher_id' => 'integer|nullable',
diff --git a/app/Http/Requests/StorePublisherRequest.php b/app/Http/Requests/StorePublisherRequest.php
index 86a65f2..2d27f7d 100644
--- a/app/Http/Requests/StorePublisherRequest.php
+++ b/app/Http/Requests/StorePublisherRequest.php
@@ -88,9 +88,10 @@ public function rules(): array
                 'min:3',
                 'max:255',
                 Rule::unique('publishers')
-                    ->where(function ($query) {
-                        return $query->where('email', $this->email)
-                            && $query->where('website', $this->website);
+                    ->where(function (\Illuminate\Database\Query\Builder $query) {
+                        $query
+                            ->where('email', $this->email)
+                            ->where('website', $this->website);
                     }),
             ],
             'email' => 'required|string|email|filled',
diff --git a/app/Http/Requests/UpdateBookRequest.php b/app/Http/Requests/UpdateBookRequest.php
index b9d9130..b7674e0 100644
--- a/app/Http/Requests/UpdateBookRequest.php
+++ b/app/Http/Requests/UpdateBookRequest.php
@@ -82,8 +82,8 @@ public function rules(): array
                 'filled',
                 Rule::unique('books')
                     ->ignore($this->books)
-                    ->where(function ($query) {
-                        return $query->where('isbn', $this->isbn);
+                    ->where(function (\Illuminate\Database\Query\Builder $query) {
+                        $query->where('isbn', $this->isbn);
                     }),
             ],
             'publisher_id' => 'integer|nullable',
diff --git a/app/Http/Requests/UpdatePublisherRequest.php b/app/Http/Requests/UpdatePublisherRequest.php
index f521a7f..813d860 100644
--- a/app/Http/Requests/UpdatePublisherRequest.php
+++ b/app/Http/Requests/UpdatePublisherRequest.php
@@ -88,9 +88,10 @@ public function rules(): array
                 'max:255',
                 Rule::unique('publishers')
                     ->ignore($this->publisher)
-                    ->where(function ($query) {
-                        return $query->where('email', $this->email)
-                            && $query->where('website', $this->website);
+                    ->where(function (\Illuminate\Database\Query\Builder $query) {
+                        $query
+                            ->where('email', $this->email)
+                            ->where('website', $this->website);
                     }),
             ],
             'email' => 'sometimes|required|string|email|filled',
diff --git a/app/Providers/AppServiceProvider.php b/app/Providers/AppServiceProvider.php
index 5988f44..1fdf18d 100644
--- a/app/Providers/AppServiceProvider.php
+++ b/app/Providers/AppServiceProvider.php
@@ -8,6 +8,7 @@
 use App\Repositories\PublisherRepository;
 use App\Services\BookService;
 use App\Services\PublisherService;
+use Illuminate\Contracts\Foundation\Application;
 use Illuminate\Support\ServiceProvider;
 
 class AppServiceProvider extends ServiceProvider
@@ -18,7 +19,7 @@ class AppServiceProvider extends ServiceProvider
     public function register(): void
     {
         $this->app->bind(BookRepositoryInterface::class, BookRepository::class);
-        $this->app->bind(BookService::class, function ($app) {
+        $this->app->bind(BookService::class, function (Application $app) {
             return new BookService(
                 $app->make(BookRepositoryInterface::class),
                 $app->make(PublisherRepositoryInterface::class),
@@ -26,7 +27,7 @@ public function register(): void
         });
 
         $this->app->bind(PublisherRepositoryInterface::class, PublisherRepository::class);
-        $this->app->bind(PublisherService::class, function ($app) {
+        $this->app->bind(PublisherService::class, function (Application $app) {
             return new PublisherService($app->make(PublisherRepositoryInterface::class));
         });
     }
diff --git a/phpstan.neon.dist b/phpstan.neon.dist
index 6fe41e8..28b0aae 100644
--- a/phpstan.neon.dist
+++ b/phpstan.neon.dist
@@ -5,8 +5,8 @@ parameters:
     paths:
         - app/
 
-    # Level 9 is the highest level
-    level: 9
+    # Level 9 is the highest numeric level
+    level: max
 
 #    ignoreErrors:
 #        - '#PHPDoc tag @var#'