diff --git a/lib/bcoin/mtx.js b/lib/bcoin/mtx.js
index be6055ca..c1435947 100644
--- a/lib/bcoin/mtx.js
+++ b/lib/bcoin/mtx.js
@@ -86,6 +86,7 @@ function MTX(options) {
   this._hashPrevouts = null;
   this._hashSequence = null;
   this._hashOutputs = null;
+  this._lastWitnessSize = 0;
 
   if (options.inputs) {
     for (i = 0; i < options.inputs.length; i++)
@@ -100,6 +101,10 @@ function MTX(options) {
 
 utils.inherits(MTX, bcoin.tx);
 
+MTX.fromOptions = function fromOptions(options) {
+  return new MTX(options);
+};
+
 /**
  * Clone the transaction.
  * @returns {MTX}
diff --git a/lib/bcoin/tx.js b/lib/bcoin/tx.js
index 6dd7bc8c..38b69342 100644
--- a/lib/bcoin/tx.js
+++ b/lib/bcoin/tx.js
@@ -124,41 +124,39 @@ TX.fromOptions = function fromOptions(data) {
  */
 
 TX.prototype.clone = function clone() {
-  var copy, i;
+  var copy = new TX();
+  var i, input, output;
 
-  copy = {
-    version: this.version,
-    flag: this.flag,
-    inputs: [],
-    outputs: [],
-    locktime: this.locktime,
-    ts: this.ts,
-    block: this.block,
-    index: this.index,
-    height: this.height
-  };
+  copy.ts = this.ts;
+  copy.block = this.block;
+  copy.index = this.index;
+  copy.height = this.height;
+
+  copy.version = this.version;
+  copy.flag = this.flag;
 
   for (i = 0; i < this.inputs.length; i++) {
-    copy.inputs.push({
-      prevout: {
-        hash: this.inputs[i].prevout.hash,
-        index: this.inputs[i].prevout.index
-      },
-      coin: this.inputs[i].coin,
-      script: this.inputs[i].script,
-      witness: this.inputs[i].witness,
-      sequence: this.inputs[i].sequence
-    });
+    input = new bcoin.input();
+    input.prevout = new bcoin.outpoint();
+    input.prevout.hash = this.inputs[i].prevout.hash;
+    input.prevout.index = this.inputs[i].prevout.index;
+    input.coin = this.inputs[i].coin;
+    input.script = this.inputs[i].script;
+    input.witness = this.inputs[i].witness;
+    input.sequence = this.inputs[i].sequence;
+    copy.inputs.push(input);
   }
 
   for (i = 0; i < this.outputs.length; i++) {
-    copy.outputs.push({
-      value: this.outputs[i].value,
-      script: this.outputs[i].script
-    });
+    output = new bcoin.output();
+    output.value = this.outputs[i].value;
+    output.script = this.outputs[i].script;
+    copy.outputs.push(output);
   }
 
-  return new TX(copy);
+  copy.locktime = this.locktime;
+
+  return copy;
 };
 
 /**
@@ -437,7 +435,9 @@ TX.prototype.signatureHash = function signatureHash(index, prev, type, version)
 
 TX.prototype.signatureHashV0 = function signatureHashV0(index, prev, type) {
   var p = new BufferWriter();
-  var i, copy;
+  var empty = new Script();
+  var witness = new bcoin.witness();
+  var i, copy, input, output;
 
   if (typeof index !== 'number')
     index = this.inputs.indexOf(index);
@@ -449,32 +449,31 @@ TX.prototype.signatureHashV0 = function signatureHashV0(index, prev, type) {
   assert(prev instanceof Script);
 
   // Clone the transaction.
-  copy = {
-    version: this.version,
-    flag: 1,
-    inputs: [],
-    outputs: [],
-    locktime: this.locktime
-  };
+  copy = new TX();
+
+  copy.version = this.version;
 
   for (i = 0; i < this.inputs.length; i++) {
-    copy.inputs.push({
-      prevout: this.inputs[i].prevout,
-      script: this.inputs[i].script,
-      sequence: this.inputs[i].sequence
-    });
+    input = new bcoin.input();
+    input.prevout = this.inputs[i].prevout;
+    input.script = this.inputs[i].script;
+    input.sequence = this.inputs[i].sequence;
+    input.witness = witness;
+    copy.inputs.push(input);
   }
 
   for (i = 0; i < this.outputs.length; i++) {
-    copy.outputs.push({
-      value: this.outputs[i].value,
-      script: this.outputs[i].script
-    });
+    output = new bcoin.output();
+    output.value = this.outputs[i].value;
+    output.script = this.outputs[i].script;
+    copy.outputs.push(output);
   }
 
+  copy.locktime = this.locktime;
+
   // Remove all signatures.
   for (i = 0; i < copy.inputs.length; i++)
-    copy.inputs[i].script = new Script();
+    copy.inputs[i].script = empty;
 
   // Remove all code separators.
   prev = prev.removeSeparators();
@@ -503,7 +502,7 @@ TX.prototype.signatureHashV0 = function signatureHashV0(index, prev, type) {
     // Null outputs that are not the at current input index.
     for (i = 0; i < copy.outputs.length; i++) {
       if (i !== index) {
-        copy.outputs[i].script = new Script();
+        copy.outputs[i].script = empty;
         copy.outputs[i].value = -1;
       }
     }
@@ -522,7 +521,7 @@ TX.prototype.signatureHashV0 = function signatureHashV0(index, prev, type) {
   }
 
   // Render the copy and append the hashtype.
-  TX(copy).toRaw(p);
+  copy.toRaw(p);
   p.writeU32(type);
 
   return utils.dsha256(p.render());