diff --git a/packages/lib/server-only/document/send-completed-email.ts b/packages/lib/server-only/document/send-completed-email.ts
index a397e47e7..f5cef426c 100644
--- a/packages/lib/server-only/document/send-completed-email.ts
+++ b/packages/lib/server-only/document/send-completed-email.ts
@@ -80,7 +80,7 @@ export const sendCompletedEmail = async ({ documentId, requestMetadata }: SendDo
       text: render(template, { plainText: true }),
       attachments: [
         {
-          filename: document.title,
+          filename: document.title.endsWith('.pdf') ? document.title : document.title + '.pdf',
           content: Buffer.from(completedDocument),
         },
       ],