diff --git a/src/Controller/AdminPages/AttachmentTypeController.php b/src/Controller/AdminPages/AttachmentTypeController.php
index 9bb37b7d..b1f59706 100644
--- a/src/Controller/AdminPages/AttachmentTypeController.php
+++ b/src/Controller/AdminPages/AttachmentTypeController.php
@@ -41,12 +41,12 @@ use Symfony\Component\Routing\Annotation\Route;
  */
 class AttachmentTypeController extends BaseAdminController
 {
-    protected $entity_class = AttachmentType::class;
-    protected $twig_template = 'AdminPages/AttachmentTypeAdmin.html.twig';
-    protected $form_class = AttachmentTypeAdminForm::class;
-    protected $route_base = 'attachment_type';
-    protected $attachment_class = AttachmentTypeAttachment::class;
-    protected $parameter_class = AttachmentTypeParameter::class;
+    protected string $entity_class = AttachmentType::class;
+    protected string $twig_template = 'AdminPages/AttachmentTypeAdmin.html.twig';
+    protected string $form_class = AttachmentTypeAdminForm::class;
+    protected string $route_base = 'attachment_type';
+    protected string $attachment_class = AttachmentTypeAttachment::class;
+    protected ?string $parameter_class = AttachmentTypeParameter::class;
 
     /**
      * @Route("/{id}", name="attachment_type_delete", methods={"DELETE"})
diff --git a/src/Controller/AdminPages/BaseAdminController.php b/src/Controller/AdminPages/BaseAdminController.php
index 3f6b78da..cf365d5c 100644
--- a/src/Controller/AdminPages/BaseAdminController.php
+++ b/src/Controller/AdminPages/BaseAdminController.php
@@ -65,12 +65,12 @@ use function Symfony\Component\Translation\t;
 
 abstract class BaseAdminController extends AbstractController
 {
-    protected $entity_class = '';
-    protected $form_class = '';
-    protected $twig_template = '';
-    protected $route_base = '';
-    protected $attachment_class = '';
-    protected $parameter_class = '';
+    protected string $entity_class = '';
+    protected string $form_class = '';
+    protected string $twig_template = '';
+    protected string $route_base = '';
+    protected string $attachment_class = '';
+    protected ?string $parameter_class = '';
 
     protected UserPasswordHasherInterface $passwordEncoder;
     protected TranslatorInterface $translator;
@@ -103,7 +103,7 @@ abstract class BaseAdminController extends AbstractController
             throw new InvalidArgumentException('You have to override the $attachment_class value with a valid Attachment class in your subclass!');
         }
 
-        if ('' === $this->parameter_class || !is_a($this->parameter_class, AbstractParameter::class, true)) {
+        if ('' === $this->parameter_class || ($this->parameter_class && !is_a($this->parameter_class, AbstractParameter::class, true))) {
             throw new InvalidArgumentException('You have to override the $parameter_class value with a valid Parameter class in your subclass!');
         }
 
diff --git a/src/Controller/AdminPages/CategoryController.php b/src/Controller/AdminPages/CategoryController.php
index df2b7012..4e170892 100644
--- a/src/Controller/AdminPages/CategoryController.php
+++ b/src/Controller/AdminPages/CategoryController.php
@@ -40,12 +40,12 @@ use Symfony\Component\Routing\Annotation\Route;
  */
 class CategoryController extends BaseAdminController
 {
-    protected $entity_class = Category::class;
-    protected $twig_template = 'AdminPages/CategoryAdmin.html.twig';
-    protected $form_class = CategoryAdminForm::class;
-    protected $route_base = 'category';
-    protected $attachment_class = CategoryAttachment::class;
-    protected $parameter_class = CategoryParameter::class;
+    protected string $entity_class = Category::class;
+    protected string $twig_template = 'AdminPages/CategoryAdmin.html.twig';
+    protected string $form_class = CategoryAdminForm::class;
+    protected string $route_base = 'category';
+    protected string $attachment_class = CategoryAttachment::class;
+    protected ?string $parameter_class = CategoryParameter::class;
 
     /**
      * @Route("/{id}", name="category_delete", methods={"DELETE"})
diff --git a/src/Controller/AdminPages/CurrencyController.php b/src/Controller/AdminPages/CurrencyController.php
index e1ae62c1..89174874 100644
--- a/src/Controller/AdminPages/CurrencyController.php
+++ b/src/Controller/AdminPages/CurrencyController.php
@@ -58,12 +58,12 @@ use Symfony\Contracts\Translation\TranslatorInterface;
  */
 class CurrencyController extends BaseAdminController
 {
-    protected $entity_class = Currency::class;
-    protected $twig_template = 'AdminPages/CurrencyAdmin.html.twig';
-    protected $form_class = CurrencyAdminForm::class;
-    protected $route_base = 'currency';
-    protected $attachment_class = CurrencyAttachment::class;
-    protected $parameter_class = CurrencyParameter::class;
+    protected string $entity_class = Currency::class;
+    protected string $twig_template = 'AdminPages/CurrencyAdmin.html.twig';
+    protected string $form_class = CurrencyAdminForm::class;
+    protected string $route_base = 'currency';
+    protected string $attachment_class = CurrencyAttachment::class;
+    protected ?string $parameter_class = CurrencyParameter::class;
 
     protected ExchangeRateUpdater $exchangeRateUpdater;
 
diff --git a/src/Controller/AdminPages/FootprintController.php b/src/Controller/AdminPages/FootprintController.php
index 21caac39..9496b157 100644
--- a/src/Controller/AdminPages/FootprintController.php
+++ b/src/Controller/AdminPages/FootprintController.php
@@ -41,12 +41,12 @@ use Symfony\Component\Routing\Annotation\Route;
  */
 class FootprintController extends BaseAdminController
 {
-    protected $entity_class = Footprint::class;
-    protected $twig_template = 'AdminPages/FootprintAdmin.html.twig';
-    protected $form_class = FootprintAdminForm::class;
-    protected $route_base = 'footprint';
-    protected $attachment_class = FootprintAttachment::class;
-    protected $parameter_class = FootprintParameter::class;
+    protected string $entity_class = Footprint::class;
+    protected string $twig_template = 'AdminPages/FootprintAdmin.html.twig';
+    protected string $form_class = FootprintAdminForm::class;
+    protected string $route_base = 'footprint';
+    protected string $attachment_class = FootprintAttachment::class;
+    protected ?string $parameter_class = FootprintParameter::class;
 
     /**
      * @Route("/{id}", name="footprint_delete", methods={"DELETE"})
diff --git a/src/Controller/AdminPages/LabelProfileController.php b/src/Controller/AdminPages/LabelProfileController.php
index 0681145b..46ee11ce 100644
--- a/src/Controller/AdminPages/LabelProfileController.php
+++ b/src/Controller/AdminPages/LabelProfileController.php
@@ -40,13 +40,13 @@ use Symfony\Component\Routing\Annotation\Route;
  */
 class LabelProfileController extends BaseAdminController
 {
-    protected $entity_class = LabelProfile::class;
-    protected $twig_template = 'AdminPages/LabelProfileAdmin.html.twig';
-    protected $form_class = LabelProfileAdminForm::class;
-    protected $route_base = 'label_profile';
-    protected $attachment_class = LabelAttachment::class;
+    protected string $entity_class = LabelProfile::class;
+    protected string $twig_template = 'AdminPages/LabelProfileAdmin.html.twig';
+    protected string $form_class = LabelProfileAdminForm::class;
+    protected string $route_base = 'label_profile';
+    protected string $attachment_class = LabelAttachment::class;
     //Just a placeholder
-    protected $parameter_class = AbstractParameter::class;
+    protected ?string $parameter_class = null;
 
     /**
      * @Route("/{id}", name="label_profile_delete", methods={"DELETE"})
diff --git a/src/Controller/AdminPages/ManufacturerController.php b/src/Controller/AdminPages/ManufacturerController.php
index 03b651f2..bd9d2c11 100644
--- a/src/Controller/AdminPages/ManufacturerController.php
+++ b/src/Controller/AdminPages/ManufacturerController.php
@@ -40,12 +40,12 @@ use Symfony\Component\Routing\Annotation\Route;
  */
 class ManufacturerController extends BaseAdminController
 {
-    protected $entity_class = Manufacturer::class;
-    protected $twig_template = 'AdminPages/ManufacturerAdmin.html.twig';
-    protected $form_class = CompanyForm::class;
-    protected $route_base = 'manufacturer';
-    protected $attachment_class = ManufacturerAttachment::class;
-    protected $parameter_class = ManufacturerParameter::class;
+    protected string $entity_class = Manufacturer::class;
+    protected string $twig_template = 'AdminPages/ManufacturerAdmin.html.twig';
+    protected string $form_class = CompanyForm::class;
+    protected string $route_base = 'manufacturer';
+    protected string $attachment_class = ManufacturerAttachment::class;
+    protected ?string $parameter_class = ManufacturerParameter::class;
 
     /**
      * @Route("/{id}", name="manufacturer_delete", methods={"DELETE"})
diff --git a/src/Controller/AdminPages/MeasurementUnitController.php b/src/Controller/AdminPages/MeasurementUnitController.php
index 3ea3962c..9b233a1c 100644
--- a/src/Controller/AdminPages/MeasurementUnitController.php
+++ b/src/Controller/AdminPages/MeasurementUnitController.php
@@ -41,12 +41,12 @@ use Symfony\Component\Routing\Annotation\Route;
  */
 class MeasurementUnitController extends BaseAdminController
 {
-    protected $entity_class = MeasurementUnit::class;
-    protected $twig_template = 'AdminPages/MeasurementUnitAdmin.html.twig';
-    protected $form_class = MeasurementUnitAdminForm::class;
-    protected $route_base = 'measurement_unit';
-    protected $attachment_class = MeasurementUnitAttachment::class;
-    protected $parameter_class = MeasurementUnitParameter::class;
+    protected string $entity_class = MeasurementUnit::class;
+    protected string $twig_template = 'AdminPages/MeasurementUnitAdmin.html.twig';
+    protected string $form_class = MeasurementUnitAdminForm::class;
+    protected string $route_base = 'measurement_unit';
+    protected string $attachment_class = MeasurementUnitAttachment::class;
+    protected ?string $parameter_class = MeasurementUnitParameter::class;
 
     /**
      * @Route("/{id}", name="measurement_unit_delete", methods={"DELETE"})
diff --git a/src/Controller/AdminPages/ProjectAdminController.php b/src/Controller/AdminPages/ProjectAdminController.php
index 982c5b6c..a97f58c8 100644
--- a/src/Controller/AdminPages/ProjectAdminController.php
+++ b/src/Controller/AdminPages/ProjectAdminController.php
@@ -41,12 +41,12 @@ use Symfony\Component\Routing\Annotation\Route;
  */
 class ProjectAdminController extends BaseAdminController
 {
-    protected $entity_class = Project::class;
-    protected $twig_template = 'AdminPages/ProjectAdmin.html.twig';
-    protected $form_class = ProjectAdminForm::class;
-    protected $route_base = 'project';
-    protected $attachment_class = ProjectAttachment::class;
-    protected $parameter_class = ProjectParameter::class;
+    protected string $entity_class = Project::class;
+    protected string $twig_template = 'AdminPages/ProjectAdmin.html.twig';
+    protected string $form_class = ProjectAdminForm::class;
+    protected string $route_base = 'project';
+    protected string $attachment_class = ProjectAttachment::class;
+    protected ?string $parameter_class = ProjectParameter::class;
 
     /**
      * @Route("/{id}", name="project_delete", methods={"DELETE"})
diff --git a/src/Controller/AdminPages/StorelocationController.php b/src/Controller/AdminPages/StorelocationController.php
index c48f7b80..a38d4ce3 100644
--- a/src/Controller/AdminPages/StorelocationController.php
+++ b/src/Controller/AdminPages/StorelocationController.php
@@ -40,12 +40,12 @@ use Symfony\Component\Routing\Annotation\Route;
  */
 class StorelocationController extends BaseAdminController
 {
-    protected $entity_class = Storelocation::class;
-    protected $twig_template = 'AdminPages/StorelocationAdmin.html.twig';
-    protected $form_class = StorelocationAdminForm::class;
-    protected $route_base = 'store_location';
-    protected $attachment_class = StorelocationAttachment::class;
-    protected $parameter_class = StorelocationParameter::class;
+    protected string $entity_class = Storelocation::class;
+    protected string $twig_template = 'AdminPages/StorelocationAdmin.html.twig';
+    protected string $form_class = StorelocationAdminForm::class;
+    protected string $route_base = 'store_location';
+    protected string $attachment_class = StorelocationAttachment::class;
+    protected ?string $parameter_class = StorelocationParameter::class;
 
     /**
      * @Route("/{id}", name="store_location_delete", methods={"DELETE"})
diff --git a/src/Controller/AdminPages/SupplierController.php b/src/Controller/AdminPages/SupplierController.php
index 643ab2e7..1939bd53 100644
--- a/src/Controller/AdminPages/SupplierController.php
+++ b/src/Controller/AdminPages/SupplierController.php
@@ -40,12 +40,12 @@ use Symfony\Component\Routing\Annotation\Route;
  */
 class SupplierController extends BaseAdminController
 {
-    protected $entity_class = Supplier::class;
-    protected $twig_template = 'AdminPages/SupplierAdmin.html.twig';
-    protected $form_class = SupplierForm::class;
-    protected $route_base = 'supplier';
-    protected $attachment_class = SupplierAttachment::class;
-    protected $parameter_class = SupplierParameter::class;
+    protected string $entity_class = Supplier::class;
+    protected string $twig_template = 'AdminPages/SupplierAdmin.html.twig';
+    protected string $form_class = SupplierForm::class;
+    protected string $route_base = 'supplier';
+    protected string $attachment_class = SupplierAttachment::class;
+    protected ?string $parameter_class = SupplierParameter::class;
 
     /**
      * @Route("/{id}", name="supplier_delete", methods={"DELETE"})
diff --git a/src/Controller/GroupController.php b/src/Controller/GroupController.php
index 63d32c7b..ee21fb6a 100644
--- a/src/Controller/GroupController.php
+++ b/src/Controller/GroupController.php
@@ -44,12 +44,12 @@ use Symfony\Component\Routing\Annotation\Route;
  */
 class GroupController extends BaseAdminController
 {
-    protected $entity_class = Group::class;
-    protected $twig_template = 'AdminPages/GroupAdmin.html.twig';
-    protected $form_class = GroupAdminForm::class;
-    protected $route_base = 'group';
-    protected $attachment_class = GroupAttachment::class;
-    protected $parameter_class = GroupParameter::class;
+    protected string $entity_class = Group::class;
+    protected string $twig_template = 'AdminPages/GroupAdmin.html.twig';
+    protected string $form_class = GroupAdminForm::class;
+    protected string $route_base = 'group';
+    protected string $attachment_class = GroupAttachment::class;
+    protected ?string $parameter_class = GroupParameter::class;
 
     /**
      * @Route("/{id}/edit/{timestamp}", requirements={"id"="\d+"}, name="group_edit")
diff --git a/src/Controller/UserController.php b/src/Controller/UserController.php
index 88e39c12..359c5a30 100644
--- a/src/Controller/UserController.php
+++ b/src/Controller/UserController.php
@@ -53,13 +53,12 @@ use Symfony\Component\Routing\Annotation\Route;
  */
 class UserController extends AdminPages\BaseAdminController
 {
-    protected $entity_class = User::class;
-    protected $twig_template = 'AdminPages/UserAdmin.html.twig';
-    protected $form_class = UserAdminForm::class;
-    protected $route_base = 'user';
-    protected $attachment_class = UserAttachment::class;
-    //Just define a value here to prevent error. It is not used.
-    protected $parameter_class = AbstractParameter::class;
+    protected string $entity_class = User::class;
+    protected string $twig_template = 'AdminPages/UserAdmin.html.twig';
+    protected string $form_class = UserAdminForm::class;
+    protected string $route_base = 'user';
+    protected string $attachment_class = UserAttachment::class;
+    protected ?string $parameter_class = null;
 
     protected function additionalActionEdit(FormInterface $form, AbstractNamedDBElement $entity): bool
     {
diff --git a/src/Form/AdminPages/BaseEntityAdminForm.php b/src/Form/AdminPages/BaseEntityAdminForm.php
index 392702c3..a28e0211 100644
--- a/src/Form/AdminPages/BaseEntityAdminForm.php
+++ b/src/Form/AdminPages/BaseEntityAdminForm.php
@@ -25,6 +25,7 @@ namespace App\Form\AdminPages;
 use App\Entity\Base\AbstractNamedDBElement;
 use App\Entity\Base\AbstractStructuralDBElement;
 use App\Entity\LabelSystem\LabelProfile;
+use App\Entity\Parameters\AbstractParameter;
 use App\Form\AttachmentFormType;
 use App\Form\ParameterType;
 use App\Form\Type\MasterPictureAttachmentType;
@@ -56,6 +57,7 @@ class BaseEntityAdminForm extends AbstractType
         parent::configureOptions($resolver);
         $resolver->setRequired('attachment_class');
         $resolver->setRequired('parameter_class');
+        $resolver->setAllowedTypes('parameter_class', ['string', 'null']);
     }
 
     public function buildForm(FormBuilderInterface $builder, array $options): void
@@ -143,7 +145,9 @@ class BaseEntityAdminForm extends AbstractType
             'empty_data' => null,
         ]);
 
-        if ($entity instanceof AbstractStructuralDBElement) {
+        if ($options['parameter_class']) {
+            $prototype = new $options['parameter_class']();
+
             $builder->add(
                 'parameters',
                 CollectionType::class,
@@ -155,7 +159,7 @@ class BaseEntityAdminForm extends AbstractType
                     'reindex_enable' => true,
                     'label' => false,
                     'by_reference' => false,
-                    'prototype_data' => new $options['parameter_class'](),
+                    'prototype_data' => $prototype,
                     'entry_options' => [
                         'data_class' => $options['parameter_class'],
                     ],