diff --git a/controllers/api.js b/controllers/api.js
index 4d6f6e0..4e8a568 100644
--- a/controllers/api.js
+++ b/controllers/api.js
@@ -133,7 +133,7 @@ router.post('/payinvoice', async function(req, res) {
       call.on('data', function(payment) {
         // payment callback
         if (payment && payment.payment_route && payment.payment_route.total_amt_msat) {
-          userBalance -= parseInt((payment.payment_route.total_fees_msat + payment.payment_route.total_amt_msat) / 1000);
+          userBalance -= parseInt((+payment.payment_route.total_fees_msat + +payment.payment_route.total_amt_msat) / 1000);
           u.saveBalance(userBalance);
           payment.pay_req = req.body.invoice;
           payment.decoded = info;