diff --git a/src/Services/InfoProviderSystem/DTOs/FileDTO.php b/src/Services/InfoProviderSystem/DTOs/FileDTO.php
index 0d1db76a..84eed0c9 100644
--- a/src/Services/InfoProviderSystem/DTOs/FileDTO.php
+++ b/src/Services/InfoProviderSystem/DTOs/FileDTO.php
@@ -28,12 +28,12 @@ namespace App\Services\InfoProviderSystem\DTOs;
  * This could be a datasheet, a 3D model, a picture or similar.
  * @see \App\Tests\Services\InfoProviderSystem\DTOs\FileDTOTest
  */
-class FileDTO
+readonly class FileDTO
 {
     /**
      * @var string The URL where to get this file
      */
-    public readonly string $url;
+    public string $url;
 
     /**
      * @param  string  $url The URL where to get this file
@@ -41,7 +41,7 @@ class FileDTO
      */
     public function __construct(
         string $url,
-        public readonly ?string $name = null,
+        public ?string $name = null,
     ) {
         //Find all occurrences of non URL safe characters and replace them with their URL encoded version.
         //We only want to replace characters which can not have a valid meaning in a URL (what would break the URL).
@@ -50,4 +50,4 @@ class FileDTO
     }
 
 
-}
\ No newline at end of file
+}
diff --git a/src/Services/InfoProviderSystem/DTOs/ParameterDTO.php b/src/Services/InfoProviderSystem/DTOs/ParameterDTO.php
index 0b54d1a9..f5868039 100644
--- a/src/Services/InfoProviderSystem/DTOs/ParameterDTO.php
+++ b/src/Services/InfoProviderSystem/DTOs/ParameterDTO.php
@@ -28,17 +28,17 @@ namespace App\Services\InfoProviderSystem\DTOs;
  * This could be a voltage, a current, a temperature or similar.
  * @see \App\Tests\Services\InfoProviderSystem\DTOs\ParameterDTOTest
  */
-class ParameterDTO
+readonly class ParameterDTO
 {
     public function __construct(
-        public readonly string $name,
-        public readonly ?string $value_text = null,
-        public readonly ?float $value_typ = null,
-        public readonly ?float $value_min = null,
-        public readonly ?float $value_max = null,
-        public readonly ?string $unit = null,
-        public readonly ?string $symbol = null,
-        public readonly ?string $group = null,
+        public string $name,
+        public ?string $value_text = null,
+        public ?float $value_typ = null,
+        public ?float $value_min = null,
+        public ?float $value_max = null,
+        public ?string $unit = null,
+        public ?string $symbol = null,
+        public ?string $group = null,
     ) {
 
     }
diff --git a/src/Services/InfoProviderSystem/DTOs/PriceDTO.php b/src/Services/InfoProviderSystem/DTOs/PriceDTO.php
index f1eb28f7..2acf3e57 100644
--- a/src/Services/InfoProviderSystem/DTOs/PriceDTO.php
+++ b/src/Services/InfoProviderSystem/DTOs/PriceDTO.php
@@ -28,21 +28,21 @@ use Brick\Math\BigDecimal;
 /**
  * This DTO represents a price for a single unit in a certain discount range
  */
-class PriceDTO
+readonly class PriceDTO
 {
-    private readonly BigDecimal $price_as_big_decimal;
+    private BigDecimal $price_as_big_decimal;
 
     public function __construct(
         /** @var float The minimum amount that needs to get ordered for this price to be valid */
-        public readonly float $minimum_discount_amount,
+        public float $minimum_discount_amount,
         /** @var string The price as string (with .) */
-        public readonly string $price,
+        public string $price,
         /** @var string The currency of the used ISO code of this price detail */
-        public readonly ?string $currency_iso_code,
+        public ?string $currency_iso_code,
         /** @var bool If the price includes tax */
-        public readonly ?bool $includes_tax = true,
+        public ?bool $includes_tax = true,
         /** @var float the price related quantity */
-        public readonly ?float $price_related_quantity = 1.0,
+        public ?float $price_related_quantity = 1.0,
     )
     {
         $this->price_as_big_decimal = BigDecimal::of($this->price);
diff --git a/src/Services/InfoProviderSystem/DTOs/PurchaseInfoDTO.php b/src/Services/InfoProviderSystem/DTOs/PurchaseInfoDTO.php
index bcd8be43..9ac142ff 100644
--- a/src/Services/InfoProviderSystem/DTOs/PurchaseInfoDTO.php
+++ b/src/Services/InfoProviderSystem/DTOs/PurchaseInfoDTO.php
@@ -27,15 +27,15 @@ namespace App\Services\InfoProviderSystem\DTOs;
  * This DTO represents a purchase information for a part (supplier name, order number and prices).
  * @see \App\Tests\Services\InfoProviderSystem\DTOs\PurchaseInfoDTOTest
  */
-class PurchaseInfoDTO
+readonly class PurchaseInfoDTO
 {
     public function __construct(
-        public readonly string $distributor_name,
-        public readonly string $order_number,
+        public string $distributor_name,
+        public string $order_number,
         /** @var PriceDTO[] */
-        public readonly array $prices,
+        public array $prices,
         /** @var string|null An url to the product page of the vendor */
-        public readonly ?string $product_url = null,
+        public ?string $product_url = null,
     )
     {
         //Ensure that the prices are PriceDTO instances
@@ -45,4 +45,4 @@ class PurchaseInfoDTO
             }
         }
     }
-}
\ No newline at end of file
+}