diff --git a/config/services.yaml b/config/services.yaml
index c6f30003..3920c570 100644
--- a/config/services.yaml
+++ b/config/services.yaml
@@ -190,6 +190,10 @@ services:
         arguments:
             $available_themes: '%partdb.available_themes%'
 
+    App\Validator\Constraints\ValidThemeValidator:
+        arguments:
+            $available_themes: '%partdb.available_themes%'
+
 
     ####################################################################################################################
     # Label system
diff --git a/src/Entity/UserSystem/User.php b/src/Entity/UserSystem/User.php
index d009d16e..56034dfd 100644
--- a/src/Entity/UserSystem/User.php
+++ b/src/Entity/UserSystem/User.php
@@ -29,6 +29,7 @@ use App\Entity\PriceInformations\Currency;
 use App\Security\Interfaces\HasPermissionsInterface;
 use App\Validator\Constraints\Selectable;
 use App\Validator\Constraints\ValidPermission;
+use App\Validator\Constraints\ValidTheme;
 use Jbtronics\TFAWebauthn\Model\LegacyU2FKeyInterface;
 use Symfony\Component\Security\Core\User\PasswordAuthenticatedUserInterface;
 use Webauthn\PublicKeyCredentialUserEntity;
@@ -77,7 +78,7 @@ class User extends AttachmentContainingDBElement implements UserInterface, HasPe
     /**
      * @var string|null The theme
      * @ORM\Column(type="string", name="config_theme", nullable=true)
-     * @Assert\Choice(choices=User::AVAILABLE_THEMES)
+     * @ValidTheme()
      */
     protected ?string $theme = null;
 
diff --git a/src/Validator/Constraints/ValidTheme.php b/src/Validator/Constraints/ValidTheme.php
new file mode 100644
index 00000000..70a32a20
--- /dev/null
+++ b/src/Validator/Constraints/ValidTheme.php
@@ -0,0 +1,32 @@
+<?php
+/*
+ * This file is part of Part-DB (https://github.com/Part-DB/Part-DB-symfony).
+ *
+ *  Copyright (C) 2019 - 2023 Jan Böhmer (https://github.com/jbtronics)
+ *
+ *  This program is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU Affero General Public License as published
+ *  by the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU Affero General Public License for more details.
+ *
+ *  You should have received a copy of the GNU Affero General Public License
+ *  along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+namespace App\Validator\Constraints;
+
+use Symfony\Component\Validator\Constraint;
+
+/**
+ * A constraint to validate the theme setting of the user.
+ * @Annotation
+ */
+class ValidTheme extends Constraint
+{
+    public string $message = 'validator.selected_theme_is_invalid';
+}
\ No newline at end of file
diff --git a/src/Validator/Constraints/ValidThemeValidator.php b/src/Validator/Constraints/ValidThemeValidator.php
new file mode 100644
index 00000000..ec437b87
--- /dev/null
+++ b/src/Validator/Constraints/ValidThemeValidator.php
@@ -0,0 +1,54 @@
+<?php
+/*
+ * This file is part of Part-DB (https://github.com/Part-DB/Part-DB-symfony).
+ *
+ *  Copyright (C) 2019 - 2023 Jan Böhmer (https://github.com/jbtronics)
+ *
+ *  This program is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU Affero General Public License as published
+ *  by the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU Affero General Public License for more details.
+ *
+ *  You should have received a copy of the GNU Affero General Public License
+ *  along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+namespace App\Validator\Constraints;
+
+use Symfony\Component\Validator\Constraint;
+use Symfony\Component\Validator\ConstraintValidator;
+use Symfony\Component\Validator\Exception\UnexpectedTypeException;
+
+class ValidThemeValidator extends ConstraintValidator
+{
+    private array $available_themes;
+
+    public function __construct(array $available_themes)
+    {
+        $this->available_themes = $available_themes;
+    }
+
+    public function validate($value, Constraint $constraint)
+    {
+        if (!$constraint instanceof ValidTheme) {
+            throw new UnexpectedTypeException($constraint, ValidTheme::class);
+        }
+
+        //Empty values are allowed
+        if (null === $value || '' === $value) {
+            return;
+        }
+
+        //If a value is set, it must be a value from the available themes list
+        if (!in_array($value, $this->available_themes, true)) {
+            $this->context->buildViolation($constraint->message)
+                ->setParameter('{{ value }}', $value)
+                ->addViolation();
+        }
+    }
+}
\ No newline at end of file