diff --git a/frontend/src/__tests__/purchase-execution-toast.test.ts b/frontend/src/__tests__/purchase-execution-toast.test.ts
index c37ebbe80..6125d7a31 100644
--- a/frontend/src/__tests__/purchase-execution-toast.test.ts
+++ b/frontend/src/__tests__/purchase-execution-toast.test.ts
@@ -1040,6 +1040,7 @@ describe('handleExecutePurchase - missing payment option (#431)', () => {
   test.each([
     ['undefined', undefined],
     ['empty string', ''],
+    ['whitespace only', '   '],
   ])('refuses with an error toast and no POST when payment is %s', async (_label, payment) => {
     const rec: Record<string, unknown> = { ...buildMinimalRec() };
     if (payment === undefined) delete rec.payment;
diff --git a/frontend/src/app.ts b/frontend/src/app.ts
index 764a0f339..b187ae818 100644
--- a/frontend/src/app.ts
+++ b/frontend/src/app.ts
@@ -368,7 +368,7 @@ export async function handleExecutePurchase(): Promise<void> {
   // option. Defaulting here would silently pick the most cash-intensive
   // schedule on a money path (issue #431).
   const recsWithPayment = localRecs.filter(
-    (r): r is typeof r & { payment: string } => !!r.payment,
+    (r): r is typeof r & { payment: string } => !!r.payment?.trim(),
   );
   const missingCount = localRecs.length - recsWithPayment.length;
   if (missingCount > 0) {