diff --git a/src/Api/Billing/Controllers/PreviewInvoiceController.cs b/src/Api/Billing/Controllers/PreviewInvoiceController.cs
index 8cde24b4fe..d55e7299d6 100644
--- a/src/Api/Billing/Controllers/PreviewInvoiceController.cs
+++ b/src/Api/Billing/Controllers/PreviewInvoiceController.cs
@@ -58,6 +58,7 @@ public class PreviewInvoiceController(
     }
 
     [HttpPost("premium/subscriptions/upgrade")]
+    [InjectUser]
     public async Task<IResult> PreviewPremiumUpgradeProrationAsync(
         [BindNever] User user,
         [FromBody] PreviewPremiumUpgradeProrationRequest request)
diff --git a/src/Core/Billing/Premium/Commands/PreviewPremiumUpgradeProrationCommand.cs b/src/Core/Billing/Premium/Commands/PreviewPremiumUpgradeProrationCommand.cs
index edb0255328..db5b907f8c 100644
--- a/src/Core/Billing/Premium/Commands/PreviewPremiumUpgradeProrationCommand.cs
+++ b/src/Core/Billing/Premium/Commands/PreviewPremiumUpgradeProrationCommand.cs
@@ -115,7 +115,6 @@ public class PreviewPremiumUpgradeProrationCommand(
         var options = new InvoiceCreatePreviewOptions
         {
             AutomaticTax = new InvoiceAutomaticTaxOptions { Enabled = true },
-            Currency = "usd",
             Customer = user.GatewayCustomerId,
             Subscription = user.GatewaySubscriptionId,
             CustomerDetails = new InvoiceCustomerDetailsOptions
diff --git a/test/Core.Test/Billing/Premium/Commands/PreviewPremiumUpgradeProrationCommandTests.cs b/test/Core.Test/Billing/Premium/Commands/PreviewPremiumUpgradeProrationCommandTests.cs
index b1f60de67e..a681797a82 100644
--- a/test/Core.Test/Billing/Premium/Commands/PreviewPremiumUpgradeProrationCommandTests.cs
+++ b/test/Core.Test/Billing/Premium/Commands/PreviewPremiumUpgradeProrationCommandTests.cs
@@ -566,7 +566,6 @@ public class PreviewPremiumUpgradeProrationCommandTests
         await _stripeAdapter.Received(1).CreateInvoicePreviewAsync(
             Arg.Is<InvoiceCreatePreviewOptions>(options =>
                 options.AutomaticTax.Enabled == true &&
-                options.Currency == "usd" &&
                 options.Customer == "cus_123" &&
                 options.Subscription == "sub_123" &&
                 options.CustomerDetails.Address.Country == "US" &&