diff --git a/lib/primitives/mtx.js b/lib/primitives/mtx.js
index f81fd308..e3141fac 100644
--- a/lib/primitives/mtx.js
+++ b/lib/primitives/mtx.js
@@ -70,11 +70,6 @@ MTX.prototype.fromOptions = function fromOptions(options) {
     this.version = options.version;
   }
 
-  if (options.flag != null) {
-    assert(util.isU8(options.flag), 'Flag must be a uint8.');
-    this.flag = options.flag;
-  }
-
   if (options.inputs) {
     assert(Array.isArray(options.inputs), 'Inputs must be an array.');
     for (const input of options.inputs)
diff --git a/lib/primitives/tx.js b/lib/primitives/tx.js
index d9de4ba1..fc3bce78 100644
--- a/lib/primitives/tx.js
+++ b/lib/primitives/tx.js
@@ -47,7 +47,6 @@ function TX(options) {
     return new TX(options);
 
   this.version = 1;
-  this.flag = 1;
   this.inputs = [];
   this.outputs = [];
   this.locktime = 0;
@@ -84,11 +83,6 @@ TX.prototype.fromOptions = function fromOptions(options) {
     this.version = options.version;
   }
 
-  if (options.flag != null) {
-    assert(util.isU8(options.flag), 'Flag must be a uint8.');
-    this.flag = options.flag;
-  }
-
   if (options.inputs) {
     assert(Array.isArray(options.inputs), 'Inputs must be an array.');
     for (const input of options.inputs)
@@ -138,7 +132,6 @@ TX.prototype.clone = function clone() {
 
 TX.prototype.inject = function inject(tx) {
   this.version = tx.version;
-  this.flag = tx.flag;
 
   for (const input of tx.inputs)
     this.inputs.push(input.clone());
@@ -2095,7 +2088,6 @@ TX.prototype.format = function format(view, entry, index) {
     date: date,
     index: index,
     version: this.version,
-    flag: this.flag,
     inputs: this.inputs.map((input) => {
       const coin = view ? view.getOutputFor(input) : null;
       return input.format(coin);
@@ -2160,7 +2152,6 @@ TX.prototype.getJSON = function getJSON(network, view, entry, index) {
     date: date,
     index: index,
     version: this.version,
-    flag: this.flag,
     inputs: this.inputs.map((input) => {
       const coin = view ? view.getCoinFor(input) : null;
       return input.getJSON(network, coin);
@@ -2182,13 +2173,11 @@ TX.prototype.getJSON = function getJSON(network, view, entry, index) {
 TX.prototype.fromJSON = function fromJSON(json) {
   assert(json, 'TX data is required.');
   assert(util.isU32(json.version), 'Version must be a uint32.');
-  assert(util.isU8(json.flag), 'Flag must be a uint8.');
   assert(Array.isArray(json.inputs), 'Inputs must be an array.');
   assert(Array.isArray(json.outputs), 'Outputs must be an array.');
   assert(util.isU32(json.locktime), 'Locktime must be a uint32.');
 
   this.version = json.version;
-  this.flag = json.flag;
 
   for (const input of json.inputs)
     this.inputs.push(Input.fromJSON(input));
@@ -2296,11 +2285,9 @@ TX.prototype.fromWitnessReader = function fromWitnessReader(br) {
 
   assert(br.readU8() === 0, 'Non-zero marker.');
 
-  let flag = br.readU8();
+  let flags = br.readU8();
 
-  assert(flag !== 0, 'Flag byte is zero.');
-
-  this.flag = flag;
+  assert(flags !== 0, 'Flags byte is zero.');
 
   const inCount = br.readVarint();
 
@@ -2315,8 +2302,8 @@ TX.prototype.fromWitnessReader = function fromWitnessReader(br) {
   let witness = 0;
   let hasWitness = false;
 
-  if (flag & 1) {
-    flag ^= 1;
+  if (flags & 1) {
+    flags ^= 1;
 
     witness = br.offset;
 
@@ -2329,7 +2316,7 @@ TX.prototype.fromWitnessReader = function fromWitnessReader(br) {
     witness = (br.offset - witness) + 2;
   }
 
-  if (flag !== 0)
+  if (flags !== 0)
     throw new Error('Unknown witness flag.');
 
   // We'll never be able to reserialize
@@ -2422,7 +2409,7 @@ TX.prototype.writeWitness = function writeWitness(bw) {
 
   bw.writeU32(this.version);
   bw.writeU8(0);
-  bw.writeU8(this.flag);
+  bw.writeU8(1);
 
   bw.writeVarint(this.inputs.length);
 
diff --git a/scripts/gen.js b/scripts/gen.js
index 00e94d9e..2489d591 100644
--- a/scripts/gen.js
+++ b/scripts/gen.js
@@ -35,7 +35,6 @@ function createGenesisBlock(options) {
 
   const tx = new TX({
     version: 1,
-    flag: 1,
     inputs: [{
       prevout: {
         hash: encoding.NULL_HASH,
diff --git a/test/script-test.js b/test/script-test.js
index 8cb3a900..cabac13c 100644
--- a/test/script-test.js
+++ b/test/script-test.js
@@ -287,7 +287,6 @@ describe('Script', function() {
         // Funding transaction.
         const prev = new TX({
           version: 1,
-          flag: 1,
           inputs: [{
             prevout: {
               hash: encoding.NULL_HASH,
@@ -307,7 +306,6 @@ describe('Script', function() {
         // Spending transaction.
         const tx = new TX({
           version: 1,
-          flag: 1,
           inputs: [{
             prevout: {
               hash: prev.hash('hex'),
@@ -329,8 +327,7 @@ describe('Script', function() {
           tx.refresh();
         }
 
-        let err;
-        let res;
+        let err, res;
         try {
           res = Script.verify(input, witness, output, tx, 0, amount, flags);
         } catch (e) {
diff --git a/test/tx-test.js b/test/tx-test.js
index 8d62a8e2..6f1735ea 100644
--- a/test/tx-test.js
+++ b/test/tx-test.js
@@ -340,7 +340,6 @@ describe('TX', function() {
     const [input, view] = createInput(consensus.MAX_MONEY + 1);
     const tx = new TX({
       version: 1,
-      flag: 1,
       inputs: [input],
       outputs: [{
         script: [],
@@ -356,7 +355,6 @@ describe('TX', function() {
     const [input, view] = createInput(consensus.MAX_MONEY);
     const tx = new TX({
       version: 1,
-      flag: 1,
       inputs: [input],
       outputs: [{
         script: [],
@@ -372,7 +370,6 @@ describe('TX', function() {
     const [input, view] = createInput(consensus.MAX_MONEY);
     const tx = new TX({
       version: 1,
-      flag: 1,
       inputs: [input],
       outputs: [{
         script: [],
@@ -388,7 +385,6 @@ describe('TX', function() {
     const [input, view] = createInput(consensus.MAX_MONEY);
     const tx = new TX({
       version: 1,
-      flag: 1,
       inputs: [input],
       outputs: [{
         script: [],
@@ -404,7 +400,6 @@ describe('TX', function() {
     const [input, view] = createInput(consensus.MAX_MONEY + 1);
     const tx = new TX({
       version: 1,
-      flag: 1,
       inputs: [input],
       outputs: [{
         script: [],
@@ -420,7 +415,6 @@ describe('TX', function() {
     const view = new CoinView();
     const tx = new TX({
       version: 1,
-      flag: 1,
       inputs: [
         createInput(Math.floor(consensus.MAX_MONEY / 2), view)[0],
         createInput(Math.floor(consensus.MAX_MONEY / 2), view)[0],
@@ -440,7 +434,6 @@ describe('TX', function() {
     const [input, view] = createInput(consensus.MAX_MONEY);
     const tx = new TX({
       version: 1,
-      flag: 1,
       inputs: [input],
       outputs: [
         {
@@ -466,7 +459,6 @@ describe('TX', function() {
     const view = new CoinView();
     const tx = new TX({
       version: 1,
-      flag: 1,
       inputs: [
         createInput(Math.floor(consensus.MAX_MONEY / 2), view)[0],
         createInput(Math.floor(consensus.MAX_MONEY / 2), view)[0],
@@ -487,7 +479,6 @@ describe('TX', function() {
 
     const tx = new TX({
       version: 1,
-      flag: 1,
       inputs: [input],
       outputs: [{
         script: [],
@@ -515,7 +506,6 @@ describe('TX', function() {
     const [input, view] = createInput(MAX_SAFE_INTEGER);
     const tx = new TX({
       version: 1,
-      flag: 1,
       inputs: [input],
       outputs: [{
         script: [],
@@ -531,7 +521,6 @@ describe('TX', function() {
     const [input, view] = createInput(consensus.MAX_MONEY);
     const tx = new TX({
       version: 1,
-      flag: 1,
       inputs: [input],
       outputs: [{
         script: [],
@@ -547,7 +536,6 @@ describe('TX', function() {
     const [input, view] = createInput(MAX_SAFE_INTEGER);
     const tx = new TX({
       version: 1,
-      flag: 1,
       inputs: [input],
       outputs: [{
         script: [],
@@ -564,7 +552,6 @@ describe('TX', function() {
       const view = new CoinView();
       const tx = new TX({
         version: 1,
-        flag: 1,
         inputs: [
           createInput(MAX, view)[0],
           createInput(MAX, view)[0],
@@ -584,7 +571,6 @@ describe('TX', function() {
       const [input, view] = createInput(consensus.MAX_MONEY);
       const tx = new TX({
         version: 1,
-        flag: 1,
         inputs: [input],
         outputs: [
           {
@@ -610,7 +596,6 @@ describe('TX', function() {
       const view = new CoinView();
       const tx = new TX({
         version: 1,
-        flag: 1,
         inputs: [
           createInput(MAX, view)[0],
           createInput(MAX, view)[0],