diff --git a/lib/bcoin/utils.js b/lib/bcoin/utils.js
index cca4a6dd..6400e167 100644
--- a/lib/bcoin/utils.js
+++ b/lib/bcoin/utils.js
@@ -543,7 +543,7 @@ utils.assert.equal = function assertEqual(l, r, msg) {
 
 utils.toBTC = function toBTC(satoshi, strict) {
   var m = new bn(10000000).mul(new bn(10));
-  var lo = satoshi.mod(m);
+  var lo;
 
   if (typeof satoshi === 'string' && /^\d+(?:\.\d+)?$/.test(satoshi)) {
     satoshi = new bn(satoshi, 10);
@@ -556,6 +556,8 @@ utils.toBTC = function toBTC(satoshi, strict) {
   if (!(satoshi instanceof bn))
     throw new Error('could not calculate btc');
 
+  lo = satoshi.mod(m);
+
   if (lo.cmpn(0) !== 0) {
     lo = lo.toString(10);
     while (lo.length < 8)