diff --git a/EnvelopeGenerator.Domain/Resources/Model.cs b/EnvelopeGenerator.Domain/Resources/Model.cs
new file mode 100644
index 00000000..d47af8ad
--- /dev/null
+++ b/EnvelopeGenerator.Domain/Resources/Model.cs
@@ -0,0 +1,7 @@
+namespace EnvelopeGenerator.Domain.Resources
+{
+    // Marker type for IStringLocalizer lookup of Resources/Model.resx.
+    public class Model
+    {
+    }
+}
diff --git a/EnvelopeGenerator.Server/EnvelopeGenerator.Server/Components/Pages/EnvelopeSenderPage.razor b/EnvelopeGenerator.Server/EnvelopeGenerator.Server/Components/Pages/EnvelopeSenderPage.razor
index 0f968fdd..cc5c2817 100644
--- a/EnvelopeGenerator.Server/EnvelopeGenerator.Server/Components/Pages/EnvelopeSenderPage.razor
+++ b/EnvelopeGenerator.Server/EnvelopeGenerator.Server/Components/Pages/EnvelopeSenderPage.razor
@@ -8,6 +8,7 @@
 @using EnvelopeGenerator.Server.Client.Services
 @using EnvelopeGenerator.Application.Common.Dto
 @using EnvelopeGenerator.Application.Common.Dto.History
+@using EnvelopeGenerator.Domain.Resources
 @using EnvelopeGenerator.Server.Services
 @using Microsoft.Extensions.Localization
 @inject EnvelopeGenerator.Server.Client.Services.EnvelopeService EnvelopeService
@@ -21,7 +22,7 @@
 @inject NavigationManager Navigation
 @inject IJSRuntime JSRuntime
 @inject AppVersionService AppVersion
-@inject IStringLocalizer<My.Resources.Model> ModelLocalizer
+@inject IStringLocalizer<Model> ModelLocalizer
 
 <link href="@AppVersion.GetVersionedUrl("css/envelope-viewer.css")" rel="stylesheet" />
 <link href="@AppVersion.GetVersionedUrl("css/sender-page.css")" rel="stylesheet" />
diff --git a/EnvelopeGenerator.Server/EnvelopeGenerator.Server/Controllers/LocalizationController.cs b/EnvelopeGenerator.Server/EnvelopeGenerator.Server/Controllers/LocalizationController.cs
index 6aa622c4..0fbb72cb 100644
--- a/EnvelopeGenerator.Server/EnvelopeGenerator.Server/Controllers/LocalizationController.cs
+++ b/EnvelopeGenerator.Server/EnvelopeGenerator.Server/Controllers/LocalizationController.cs
@@ -92,10 +92,10 @@ public class LocalizationController : ControllerBase
             var cookieValue = Request.Cookies[CookieRequestCultureProvider.DefaultCookieName];
 
             if (string.IsNullOrEmpty(cookieValue))
-                return null;
+                return "de-DE";
 
             var culture = CookieRequestCultureProvider.ParseCookieValue(cookieValue)?.Cultures[0];
-            return culture?.Value ?? null;
+            return culture?.Value ?? "de-DE";
         }
         set
         {
@@ -118,4 +118,4 @@ public class LocalizationController : ControllerBase
             }
         }
     }
-}
\ No newline at end of file
+}
diff --git a/EnvelopeGenerator.Server/EnvelopeGenerator.Server/Program.cs b/EnvelopeGenerator.Server/EnvelopeGenerator.Server/Program.cs
index 584049e6..782ad06d 100644
--- a/EnvelopeGenerator.Server/EnvelopeGenerator.Server/Program.cs
+++ b/EnvelopeGenerator.Server/EnvelopeGenerator.Server/Program.cs
@@ -410,16 +410,16 @@ try
     // Set CORS policy
     app.UseCors("AllowSpecificOriginsPolicy");
 
-    // Localization
-    string[] supportedCultureNames = ["de-DE", "en-US"];
-    IList<CultureInfo> list = [.. supportedCultureNames.Select(cn => new CultureInfo(cn))];
-    var cultureInfo = list.FirstOrDefault() ?? throw new InvalidOperationException("There is no supported culture.");
+    // Localization (fixed to German for now; persisted via cookie)
+    var defaultCulture = new CultureInfo("de-DE");
+    IList<CultureInfo> list = [defaultCulture];
     var requestLocalizationOptions = new RequestLocalizationOptions
     {
+        DefaultRequestCulture = new RequestCulture(defaultCulture),
         SupportedCultures = list,
-        SupportedUICultures = list
+        SupportedUICultures = list,
+        RequestCultureProviders = [new CookieRequestCultureProvider()]
     };
-    requestLocalizationOptions.RequestCultureProviders.Add(new QueryStringRequestCultureProvider());
     app.UseRequestLocalization(requestLocalizationOptions);
 
     app.UseHttpsRedirection();