diff --git a/index.js b/index.js
index a31b5886f..7c4f0cc21 100644
--- a/index.js
+++ b/index.js
@@ -51,6 +51,7 @@ bitcore.deps.elliptic = require('elliptic');
 
 // Internal usage, exposed for testing/advanced tweaking
 bitcore._HDKeyCache = require('./lib/hdkeycache');
+bitcore.Transaction.sighash = require('./lib/transaction/sighash');
 
 // module information
 bitcore.version = 'v'+require('./package.json').version;