diff --git a/src/transaction.js b/src/transaction.js
index f346125..5470dcd 100644
--- a/src/transaction.js
+++ b/src/transaction.js
@@ -361,7 +361,7 @@ Transaction.prototype.signWithKeys = function(keys, outputs, type) {
 Transaction.prototype.signScriptSig = function(index, script, key, type) {
   type = type || SIGHASH_ALL
 
-  assert(Number.isFinite(index) && (index >= 0), 'Invalid vin index')
+  assert((index >= 0), 'Invalid vin index')
   assert(script instanceof Script, 'Invalid Script object')
   assert(key instanceof ECKey, 'Invalid private key')
 //  assert.equal(type & 0x7F, type, 'Invalid type') // TODO