diff --git a/src/transaction_builder.js b/src/transaction_builder.js
index a08af72..aa716bf 100644
--- a/src/transaction_builder.js
+++ b/src/transaction_builder.js
@@ -408,7 +408,7 @@ TransactionBuilder.prototype.sign = function (index, keyPair, redeemScript, hash
     input.signatures[i] = signature
 
     return true
-  }, this), 'key pair cannot sign for this input')
+  }), 'key pair cannot sign for this input')
 }
 
 module.exports = TransactionBuilder