1 files changed, 1 insertions, 0 deletions
diff --git a/lib/invoices.js b/lib/invoices.js
index 89c4f3d6..633072f3 100644
--- a/lib/invoices.js
+++ b/lib/invoices.js
@@ -40,6 +40,7 @@ export let generate = async ({ invoice, user, sender, }) => {
   if (!rate) rate = store.rates[currency];
   if (fiat) amount = Math.round((SATS * fiat) / rate);
   if (amount < 0) fail("invalid amount");
+  if (tip< 0) fail("invalid tip");
   if (memo && memo.length > 200) fail("memo too long");
 
   let id = v4();