diff --git a/controllers/api.js b/controllers/api.js
index ab2760b..7e51b10 100644
--- a/controllers/api.js
+++ b/controllers/api.js
@@ -187,7 +187,7 @@ router.post('/payinvoice', async function(req, res) {
         // payment callback
         await u.unlockFunds(req.body.invoice);
         if (payment && payment.payment_route && payment.payment_route.total_amt_msat) {
-          payment.payment_route.total_fees += Math.floor(+payment.payment_route.total_amt * 0.01);
+          payment.payment_route.total_fees = +payment.payment_route.total_fees + Math.floor(+payment.payment_route.total_amt * 0.01);
           userBalance -= +payment.payment_route.total_fees + +payment.payment_route.total_amt;
           u.saveBalance(userBalance);
           payment.pay_req = req.body.invoice;