diff --git a/lib/messages/builder.js b/lib/messages/builder.js
index cc25690..33f1cfa 100644
--- a/lib/messages/builder.js
+++ b/lib/messages/builder.js
@@ -10,54 +10,53 @@ function builder(options) {
     options = {};
   }
 
-  var magicNumber = options.magicNumber;
-  if (!magicNumber) {
-    magicNumber = bitcore.Networks.defaultNetwork.networkMagic.readUInt32LE(0);
+  if (!options.magicNumber) {
+    options.magicNumber = bitcore.Networks.defaultNetwork.networkMagic.readUInt32LE(0);
   }
-  var Block = options.Block || bitcore.Block;
-  var BlockHeader = options.BlockHeader || bitcore.BlockHeader;
-  var Transaction = options.Transaction || bitcore.Transaction;
-  var MerkleBlock = options.MerkleBlock || bitcore.MerkleBlock;
-  var protocolVersion = options.protocolVersion || 70000;
+
+  options.Block = options.Block || bitcore.Block;
+  options.BlockHeader = options.BlockHeader || bitcore.BlockHeader;
+  options.Transaction = options.Transaction || bitcore.Transaction;
+  options.MerkleBlock = options.MerkleBlock || bitcore.MerkleBlock;
+  options.protocolVersion = options.protocolVersion || 70000;
 
   var exported = {
     constructors: {
-      Block: Block,
-      BlockHeader: BlockHeader,
-      Transaction: Transaction,
-      MerkleBlock: MerkleBlock
+      Block: options.Block,
+      BlockHeader: options.BlockHeader,
+      Transaction: options.Transaction,
+      MerkleBlock: options.MerkleBlock
     },
     defaults: {
-      protocolVersion: protocolVersion,
-      magicNumber: magicNumber
+      protocolVersion: options.protocolVersion,
+      magicNumber: options.magicNumber
+    },
+    commandsMap: {
+      version: 'Version',
+      verack: 'VerAck',
+      ping: 'Ping',
+      pong: 'Pong',
+      block: 'Block',
+      tx: 'Transaction',
+      getdata: 'GetData',
+      headers: 'Headers',
+      notfound: 'NotFound',
+      inv: 'Inventory',
+      addr: 'Address',
+      alert: 'Alert',
+      reject: 'Reject',
+      merkleblock: 'MerkleBlock',
+      filterload: 'FilterLoad',
+      filteradd: 'FilterAdd',
+      filterclear: 'FilterClear',
+      getblocks: 'GetBlocks',
+      getheaders: 'GetHeaders',
+      mempool: 'MemPool',
+      getaddr: 'GetAddr'
     },
     commands: {}
   };
 
-  exported.commandsMap = {
-    version: 'Version',
-    verack: 'VerAck',
-    ping: 'Ping',
-    pong: 'Pong',
-    block: 'Block',
-    tx: 'Transaction',
-    getdata: 'GetData',
-    headers: 'Headers',
-    notfound: 'NotFound',
-    inv: 'Inventory',
-    addr: 'Address',
-    alert: 'Alert',
-    reject: 'Reject',
-    merkleblock: 'MerkleBlock',
-    filterload: 'FilterLoad',
-    filteradd: 'FilterAdd',
-    filterclear: 'FilterClear',
-    getblocks: 'GetBlocks',
-    getheaders: 'GetHeaders',
-    mempool: 'MemPool',
-    getaddr: 'GetAddr'
-  };
-
   for (var key in exported.commandsMap) {
     exported.commands[key] = require('./commands/' + key)(options);
   }