diff --git a/src/actions/processor/index.js b/src/actions/processor/index.js
index a258a84..49685c8 100644
--- a/src/actions/processor/index.js
+++ b/src/actions/processor/index.js
@@ -99,7 +99,7 @@ function appendToSheet(ctx, sheet, record, sheetName = 'private-data') {
   // if all properties of the first record are empty, it's a new sheet with no data
   // use the ordered record as the header row to avoid an empty row between the header and data
   // otherwise, append the ordered record to the data array
-  if (Object.values(dest.data[0]).every((value) => value === '')) {
+  if (Object.values(dest.data[0] ?? {}).every((value) => value === '')) {
     dest.data[0] = orderedRecord;
   } else {
     dest.data.push(orderedRecord);
diff --git a/test/processor.test.js b/test/processor.test.js
index cfe84f1..e96b39b 100644
--- a/test/processor.test.js
+++ b/test/processor.test.js
@@ -227,13 +227,24 @@ describe('processor action', () => {
     });
 
     test('uses deadletter path when folder has no entries', async () => {
-      mockMakeContext.mockResolvedValue(makeCtx());
+      const ctx = makeCtx();
+      mockMakeContext.mockResolvedValue(ctx);
       mockListFolder.mockResolvedValue([]);
 
       const result = await main({});
-      // empty entries → deadletter path; also means new sheet (INITIAL_SHEET)
-      // which has an empty data array, causing appendToSheet to error
-      expect(result.error.statusCode).toBe(500);
+      expect(result.statusCode).toBe(200);
+      expect(mockUpdateSheet).toHaveBeenCalledWith(
+        ctx,
+        `/incoming/deadletter/contact-us/${YEAR}.json`,
+        expect.objectContaining({
+          ':private': expect.objectContaining({
+            'private-data': expect.objectContaining({
+              total: 1,
+              data: [expect.objectContaining({ name: 'John' })],
+            }),
+          }),
+        }),
+      );
     });
   });