diff --git a/src/store/delivery/attachments.js b/src/store/delivery/attachments.js
index 43a1afe..39155c6 100644
--- a/src/store/delivery/attachments.js
+++ b/src/store/delivery/attachments.js
@@ -152,7 +152,7 @@ export async function insertAttachments(pool, tx, sql, manifestId, files) {
 
     // Generate thumbnail server-side (e.g. pdftocairo + sharp for PDF)
     const { thumbavif, thumbx, thumby } = await generateDocumentThumb(a.content, a.mimetype, { filename: a.name });
-
+    
     const fileRes = await request(pool, tx)
       .input('hash', a.hash)
       .input('mimetype', a.mimetype)
diff --git a/src/util/generateDocumentThumb.js b/src/util/generateDocumentThumb.js
index e024040..4b986f9 100644
--- a/src/util/generateDocumentThumb.js
+++ b/src/util/generateDocumentThumb.js
@@ -9,7 +9,10 @@ const THUMB_MAX = 200;
  * @returns {Promise<Buffer>}
  */
 async function renderPdfPageToPng(pdfBuffer) {
-  const images = await pdfToPng(pdfBuffer, { dpi: 150, singleFile: true });
+  // The WASM converter may transfer (and detach) its input ArrayBuffer. Give it
+  // an isolated copy so the upload buffer remains usable by SQL and logging.
+  const pdfBytes = new Uint8Array(pdfBuffer);
+  const images = await pdfToPng(pdfBytes, { dpi: 150, singleFile: true });
   if (!images || images.length === 0 || !images[0].data) {
     throw new Error('pdfconvert-wasm produced no image output');
   }