diff --git a/lib/messages/builder.js b/lib/messages/builder.js
index 12b5faf..bdaf61b 100644
--- a/lib/messages/builder.js
+++ b/lib/messages/builder.js
@@ -18,7 +18,7 @@ function builder(options) {
 
   options.Block = options.Block || fcoin.Block;
   options.BlockHeader = options.BlockHeader || bitcore.BlockHeader;
-  options.Transaction = options.Transaction || fcoin.Transaction;
+  options.Transaction = options.Transaction || fcoin.TX;
   options.MerkleBlock = options.MerkleBlock || bitcore.MerkleBlock;
   options.protocolVersion = options.protocolVersion || 70001;