diff --git a/composer.json b/composer.json
index cd9552e..7401906 100644
--- a/composer.json
+++ b/composer.json
@@ -3,6 +3,7 @@
     "description": "A Symfony bundle for knplabs/php-json-schema",
     "type": "library",
     "license": "MIT",
+    "minimum-stability": "dev",
     "autoload": {
         "psr-4": {
             "Knp\\JsonSchemaBundle\\": "src/"
@@ -16,10 +17,13 @@
     ],
     "require": {
         "php": ">=8.0",
-        "knplabs/php-json-schema": ">=0.0.3",
+        "knplabs/php-json-schema": ">=0.0.4",
         "zircote/swagger-php": ">=4.4",
         "symfony/http-kernel": ">=6.0",
         "symfony/dependency-injection": ">=6.0",
         "symfony/config": ">=6.0"
+    },
+    "require-dev": {
+        "vimeo/psalm": "5.x-dev"
     }
 }
diff --git a/psalm.xml b/psalm.xml
new file mode 100644
index 0000000..7c0333d
--- /dev/null
+++ b/psalm.xml
@@ -0,0 +1,15 @@
+<?xml version="1.0"?>
+<psalm
+    errorLevel="7"
+    resolveFromConfigFile="true"
+    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+    xmlns="https://getpsalm.org/schema/config"
+    xsi:schemaLocation="https://getpsalm.org/schema/config vendor/vimeo/psalm/config.xsd"
+>
+    <projectFiles>
+        <directory name="src" />
+        <ignoreFiles>
+            <directory name="vendor" />
+        </ignoreFiles>
+    </projectFiles>
+</psalm>
diff --git a/src/DependencyInjection/JsonSchemaExtension.php b/src/DependencyInjection/JsonSchemaExtension.php
index 0587dcb..f55dedc 100644
--- a/src/DependencyInjection/JsonSchemaExtension.php
+++ b/src/DependencyInjection/JsonSchemaExtension.php
@@ -12,7 +12,7 @@
 
 class JsonSchemaExtension extends Extension
 {
-    public function load(array $config, ContainerBuilder $container)
+    public function load(array $configs, ContainerBuilder $container): void
     {
         $loader = new XmlFileLoader(
             $container,
diff --git a/src/OpenApi/Annotation/JsonSchema.php b/src/OpenApi/Annotation/JsonSchema.php
index 5000a0c..305a5ef 100644
--- a/src/OpenApi/Annotation/JsonSchema.php
+++ b/src/OpenApi/Annotation/JsonSchema.php
@@ -10,7 +10,7 @@
 class JsonSchema extends Schema
 {
     /**
-     * @var array<string>
+     * @var array<mixed>
      */
     public static $_required = ['schema'];
 
@@ -34,10 +34,10 @@ public function __construct(array $properties)
         $this->required = $jsonSchema['required'] ?? false;
         $this->additionalProperties = $jsonSchema['additionalProperties'] ?? true;
 
-        $this->properties = array_map(function ($name, $property) {
+        $this->properties = array_map(function ($name, array $property) {
             if (\array_key_exists('oneOf', $property)) {
                 $property['oneOf'] = array_map(
-                    fn ($schema) => new Schema($schema),
+                    fn (array $schema) => new Schema($schema),
                     $property['oneOf']
                 );
             }
diff --git a/src/OpenApi/Attributes/JsonSchema.php b/src/OpenApi/Attributes/JsonSchema.php
index 30479c7..dbb02f2 100644
--- a/src/OpenApi/Attributes/JsonSchema.php
+++ b/src/OpenApi/Attributes/JsonSchema.php
@@ -30,10 +30,10 @@ public function __construct(array $properties)
         $this->required = $jsonSchema['required'] ?? false;
         $this->additionalProperties = $jsonSchema['additionalProperties'] ?? true;
 
-        $this->properties = array_map(function ($name, $property) {
+        $this->properties = array_map(function ($name, array $property) {
             if (\array_key_exists('oneOf', $property)) {
                 $property['oneOf'] = array_map(
-                    fn ($schema) => new Schema($schema),
+                    fn (object $schema) => new Schema($schema),
                     $property['oneOf']
                 );
             }
diff --git a/src/RequestHandler.php b/src/RequestHandler.php
index a6d016f..79a434c 100644
--- a/src/RequestHandler.php
+++ b/src/RequestHandler.php
@@ -5,6 +5,7 @@
 namespace Knp\JsonSchemaBundle;
 
 use Knp\JsonSchema\Collection;
+use Knp\JsonSchema\JsonSchemaInterface;
 use Knp\JsonSchema\Validator;
 use Knp\JsonSchemaBundle\Exception\JsonSchemaException;
 use Symfony\Component\HttpFoundation\Request;
@@ -20,16 +21,21 @@ class RequestHandler
         'application/json;charset=utf-8',
     ];
 
+    private Collection $schemas;
+    private Validator $validator;
+
     public function __construct(
-        private readonly Collection $schemas,
-        private readonly Validator $validator
+        Collection $schemas,
+        Validator $validator
     ) {
+        $this->schemas = $schemas;
+        $this->validator = $validator;
     }
 
     /**
      * @template T
      *
-     * @param class-string<JsonSchema<T>> $schemaClass
+     * @param class-string<JsonSchemaInterface<T>> $schemaClass
      *
      * @return T
      */