diff --git a/app/api/skatteverket/tax-payments/[period]/payment-file/route.ts b/app/api/skatteverket/tax-payments/[period]/payment-file/route.ts
index 6efce6a7..8c07d728 100644
--- a/app/api/skatteverket/tax-payments/[period]/payment-file/route.ts
+++ b/app/api/skatteverket/tax-payments/[period]/payment-file/route.ts
@@ -218,7 +218,9 @@ export const GET = withRouteContext<{ params: Promise<{ period: string }> }>(
     .eq('id', agi.id)
     .eq('company_id', companyId)
 
-  return new Response(fileContent, {
+  // Buffer is not assignable to BodyInit under the strict build tsconfig
+  // (Buffer<ArrayBufferLike>); the repo convention is a Uint8Array view.
+  return new Response(new Uint8Array(fileContent), {
     headers: {
       'Content-Type': contentType,
       'Content-Disposition': `attachment; filename="${filename}"`,