diff --git a/composer.json b/composer.json
index b01e3e8..450d6f1 100644
--- a/composer.json
+++ b/composer.json
@@ -24,7 +24,7 @@
         "vimeo/psalm": "^5.4",
         "symfony/cache": "^5.3||^6.2",
         "php-parallel-lint/php-parallel-lint": "^1.3.2",
-        "phpstan/phpstan": "^1.12"
+        "phpstan/phpstan": "^1.12 || ^2.0"
     },
     "suggest": {
         "ramsey/uuid-doctrine": "Support for an UUID Doctrine type"
diff --git a/src/Attribute/Entity.php b/src/Attribute/Entity.php
index fc2eddf..27c80b1 100644
--- a/src/Attribute/Entity.php
+++ b/src/Attribute/Entity.php
@@ -30,7 +30,7 @@ public function __construct(
     ) {
     }
 
-    public function getGroup(): string|null
+    public function getGroup(): string
     {
         return $this->group;
     }
diff --git a/src/Input/InputFactory.php b/src/Input/InputFactory.php
index cd068c8..d454223 100644
--- a/src/Input/InputFactory.php
+++ b/src/Input/InputFactory.php
@@ -59,8 +59,8 @@ public function get(string $id, array $requiredFields = [], array $optionalField
     }
 
     /**
-     * @param string[]                     $optionalFields
-     * @param array<int, InputObjectField> $fields
+     * @param string[]                            $optionalFields
+     * @param array<int|string, InputObjectField> $fields
      */
     protected function addOptionalFields(
         mixed $targetEntity,
@@ -94,8 +94,8 @@ protected function addOptionalFields(
     }
 
     /**
-     * @param string[]                     $requiredFields
-     * @param array<int, InputObjectField> $fields
+     * @param string[]                            $requiredFields
+     * @param array<int|string, InputObjectField> $fields
      */
     protected function addRequiredFields(
         mixed $targetEntity,
@@ -128,7 +128,7 @@ protected function addRequiredFields(
         }
     }
 
-    /** @param array<int, InputObjectField> $fields */
+    /** @param array<int|string, InputObjectField> $fields */
     protected function addAllFieldsAsRequired(mixed $targetEntity, array &$fields): void
     {
         foreach ($this->entityManager->getClassMetadata($targetEntity->getEntityClass())->getFieldNames() as $fieldName) {