diff --git a/lib/workers/child-browser.js b/lib/workers/child-browser.js
index fe3e8e5e..aac029c1 100644
--- a/lib/workers/child-browser.js
+++ b/lib/workers/child-browser.js
@@ -16,16 +16,15 @@ const util = require('../utils/util');
  * @constructor
  * @ignore
  * @param {String} file
- * @param {Object} env
  */
 
-function Child(file, env) {
+function Child(file) {
   if (!(this instanceof Child))
-    return new Child(file, env);
+    return new Child(file);
 
   EventEmitter.call(this);
 
-  this.init(file, env);
+  this.init(file);
 }
 
 util.inherits(Child, EventEmitter);
@@ -42,9 +41,10 @@ Child.hasSupport = function hasSupport() {
 /**
  * Initialize child process. Bind to events.
  * @private
+ * @param {String} file
  */
 
-Child.prototype.init = function init(file, env) {
+Child.prototype.init = function init(file) {
   this.child = new global.Worker(file);
 
   this.child.onerror = (event) => {
@@ -65,8 +65,6 @@ Child.prototype.init = function init(file, env) {
     }
     this.emit('data', data);
   };
-
-  this.child.postMessage(JSON.stringify(env));
 };
 
 /**
diff --git a/lib/workers/child.js b/lib/workers/child.js
index 55ca428e..67dcf9ba 100644
--- a/lib/workers/child.js
+++ b/lib/workers/child.js
@@ -19,19 +19,18 @@ let exitBound = false;
  * @alias module:workers.Child
  * @constructor
  * @param {String} file
- * @param {Object} env
  */
 
-function Child(file, env) {
+function Child(file) {
   if (!(this instanceof Child))
-    return new Child(file, env);
+    return new Child(file);
 
   EventEmitter.call(this);
 
   bindExit();
   children.add(this);
 
-  this.init(file, env);
+  this.init(file);
 }
 
 util.inherits(Child, EventEmitter);
@@ -48,13 +47,13 @@ Child.hasSupport = function hasSupport() {
 /**
  * Initialize child process (node.js).
  * @private
+ * @param {String} file
  */
 
-Child.prototype.init = function init(file, env) {
+Child.prototype.init = function init(file) {
   let bin = process.argv[0];
   let filename = path.resolve(__dirname, file);
-  let environ = Object.assign({}, process.env, env);
-  let options = { stdio: 'pipe', env: environ };
+  let options = { stdio: 'pipe', env: process.env };
 
   this.child = cp.spawn(bin, [filename], options);
 
diff --git a/lib/workers/master.js b/lib/workers/master.js
index 1bc77155..a003f5f0 100644
--- a/lib/workers/master.js
+++ b/lib/workers/master.js
@@ -32,7 +32,6 @@ function Master() {
   this.parent = new Parent();
   this.framer = new Framer();
   this.parser = new Parser();
-  this.env = {};
   this.listening = false;
   this.color = false;
 
@@ -69,6 +68,16 @@ Master.prototype.init = function init() {
   });
 };
 
+/**
+ * Set environment.
+ * @param {Object} env
+ */
+
+Master.prototype.setEnv = function setEnv(env) {
+  this.color = env.BCOIN_WORKER_ISTTY === '1';
+  this.set(env.BCOIN_WORKER_NETWORK);
+};
+
 /**
  * Set primary network.
  * @param {NetworkType|Network} network
@@ -130,18 +139,12 @@ Master.prototype.log = function log(...items) {
 
 /**
  * Listen for messages from master process (only if worker).
- * @param {Object} env
- * @returns {Master}
  */
 
-Master.prototype.listen = function listen(env) {
+Master.prototype.listen = function listen() {
   assert(!this.listening, 'Already listening.');
 
-  this.env = env;
   this.listening = true;
-  this.color = +env.BCOIN_WORKER_ISTTY === 1;
-
-  this.set(env.BCOIN_WORKER_NETWORK);
 
   util.log = this.log.bind(this);
   util.error = util.log;
@@ -157,8 +160,6 @@ Master.prototype.listen = function listen(env) {
       this.emit('error', e);
     }
   });
-
-  return this;
 };
 
 /**
@@ -171,6 +172,9 @@ Master.prototype.handlePacket = function handlePacket(packet) {
   let result;
 
   switch (packet.cmd) {
+    case packets.types.ENV:
+      this.setEnv(packet.env);
+      break;
     case packets.types.EVENT:
       this.emit('event', packet.items);
       this.emit.apply(this, packet.items);
diff --git a/lib/workers/packets.js b/lib/workers/packets.js
index 1d801789..bbc65455 100644
--- a/lib/workers/packets.js
+++ b/lib/workers/packets.js
@@ -27,26 +27,27 @@ const CoinView = require('../coins/coinview');
  */
 
 const packetTypes = {
-  EVENT: 0,
-  LOG: 1,
-  ERROR: 2,
-  ERRORRESULT: 3,
-  VERIFY: 4,
-  VERIFYRESULT: 5,
-  SIGN: 6,
-  SIGNRESULT: 7,
-  VERIFYINPUT: 8,
-  VERIFYINPUTRESULT: 9,
-  SIGNINPUT: 10,
-  SIGNINPUTRESULT: 11,
-  ECVERIFY: 12,
-  ECVERIFYRESULT: 13,
-  ECSIGN: 14,
-  ECSIGNRESULT: 15,
-  MINE: 16,
-  MINERESULT: 17,
-  SCRYPT: 18,
-  SCRYPTRESULT: 19
+  ENV: 0,
+  EVENT: 1,
+  LOG: 2,
+  ERROR: 3,
+  ERRORRESULT: 4,
+  VERIFY: 5,
+  VERIFYRESULT: 6,
+  SIGN: 7,
+  SIGNRESULT: 8,
+  VERIFYINPUT: 9,
+  VERIFYINPUTRESULT: 10,
+  SIGNINPUT: 11,
+  SIGNINPUTRESULT: 12,
+  ECVERIFY: 13,
+  ECVERIFYRESULT: 14,
+  ECSIGN: 15,
+  ECSIGNRESULT: 16,
+  MINE: 17,
+  MINERESULT: 18,
+  SCRYPT: 19,
+  SCRYPTRESULT: 20
 };
 
 /**
@@ -66,6 +67,37 @@ Packet.prototype.toWriter = function toWriter() {
   throw new Error('Abstract method.');
 };
 
+/**
+ * EnvPacket
+ * @constructor
+ */
+
+function EnvPacket(env) {
+  Packet.call(this);
+  this.env = env || {};
+  this.json = JSON.stringify(this.env);
+}
+
+util.inherits(EnvPacket, Packet);
+
+EnvPacket.prototype.cmd = packetTypes.ENV;
+
+EnvPacket.prototype.getSize = function getSize() {
+  return encoding.sizeVarString(this.json, 'utf8');
+};
+
+EnvPacket.prototype.toWriter = function toWriter(bw) {
+  bw.writeVarString(this.json, 'utf8');
+};
+
+EnvPacket.fromRaw = function fromRaw(data) {
+  let br = new BufferReader(data, true);
+  let packet = new EnvPacket();
+  packet.json = br.readVarString('utf8');
+  packet.env = JSON.parse(packet.json);
+  return packet;
+};
+
 /**
  * EventPacket
  * @constructor
@@ -92,7 +124,8 @@ EventPacket.prototype.toWriter = function toWriter(bw) {
 EventPacket.fromRaw = function fromRaw(data) {
   let br = new BufferReader(data, true);
   let packet = new EventPacket();
-  packet.items = JSON.parse(br.readVarString('utf8'));
+  packet.json = br.readVarString('utf8');
+  packet.items = JSON.parse(packet.json);
   return packet;
 };
 
@@ -141,24 +174,68 @@ ErrorPacket.prototype.cmd = packetTypes.ERROR;
 
 ErrorPacket.prototype.getSize = function getSize() {
   let size = 0;
+
   size += encoding.sizeVarString(this.error.message + '', 'utf8');
   size += encoding.sizeVarString(this.error.stack + '', 'utf8');
-  size += encoding.sizeVarString((this.error.type || ''), 'utf8');
+  size += encoding.sizeVarString(this.error.type || '', 'utf8');
+
+  switch (typeof this.error.code) {
+    case 'number':
+      size += 1;
+      size += 4;
+      break;
+    case 'string':
+      size += 1;
+      size += encoding.sizeVarString(this.error.code, 'utf8');
+      break;
+    default:
+      size += 1;
+      break;
+  }
+
   return size;
 };
 
 ErrorPacket.prototype.toWriter = function toWriter(bw) {
   bw.writeVarString(this.error.message + '', 'utf8');
   bw.writeVarString(this.error.stack + '', 'utf8');
-  bw.writeVarString((this.error.type || ''), 'utf8');
+  bw.writeVarString(this.error.type || '', 'utf8');
+
+  switch (typeof this.error.code) {
+    case 'number':
+      bw.writeU8(2);
+      bw.write32(this.error.code);
+      break;
+    case 'string':
+      bw.writeU8(1);
+      bw.writeVarString(this.error.code, 'utf8');
+      break;
+    default:
+      bw.writeU8(0);
+      break;
+  }
 };
 
 ErrorPacket.fromRaw = function fromRaw(data) {
   let br = new BufferReader(data, true);
   let packet = new ErrorPacket();
+
   packet.error.message = br.readVarString('utf8');
   packet.error.stack = br.readVarString('utf8');
   packet.error.type = br.readVarString('utf8');
+
+  switch (br.readU8()) {
+    case 2:
+      packet.error.code = br.read32();
+      break;
+    case 1:
+      packet.error.code = br.readVarString('utf8');
+      break;
+    default:
+      packet.error.code = null;
+      break;
+  }
+
   return packet;
 };
 
@@ -168,37 +245,13 @@ ErrorPacket.fromRaw = function fromRaw(data) {
  */
 
 function ErrorResultPacket(error) {
-  Packet.call(this);
-  this.error = error || new Error();
+  ErrorPacket.call(this, error);
 }
 
-util.inherits(ErrorResultPacket, Packet);
+util.inherits(ErrorResultPacket, ErrorPacket);
 
 ErrorResultPacket.prototype.cmd = packetTypes.ERRORRESULT;
 
-ErrorResultPacket.prototype.getSize = function getSize() {
-  let size = 0;
-  size += encoding.sizeVarString(this.error.message + '', 'utf8');
-  size += encoding.sizeVarString(this.error.stack + '', 'utf8');
-  size += encoding.sizeVarString((this.error.type || ''), 'utf8');
-  return size;
-};
-
-ErrorResultPacket.prototype.toWriter = function toWriter(bw) {
-  bw.writeVarString(this.error.message + '', 'utf8');
-  bw.writeVarString(this.error.stack + '', 'utf8');
-  bw.writeVarString((this.error.type || ''), 'utf8');
-};
-
-ErrorResultPacket.fromRaw = function fromRaw(data) {
-  let br = new BufferReader(data, true);
-  let packet = new ErrorResultPacket();
-  packet.error.message = br.readVarString('utf8');
-  packet.error.stack = br.readVarString('utf8');
-  packet.error.type = br.readVarString('utf8');
-  return packet;
-};
-
 /**
  * VerifyPacket
  * @constructor
@@ -894,6 +947,7 @@ ScryptResultPacket.fromRaw = function fromRaw(data) {
  */
 
 exports.types = packetTypes;
+exports.EnvPacket = EnvPacket;
 exports.EventPacket = EventPacket;
 exports.LogPacket = LogPacket;
 exports.ErrorPacket = ErrorPacket;
diff --git a/lib/workers/parser.js b/lib/workers/parser.js
index fa844ae8..d3c74b09 100644
--- a/lib/workers/parser.js
+++ b/lib/workers/parser.js
@@ -133,6 +133,8 @@ Parser.prototype.parseHeader = function parseHeader(data) {
 
 Parser.prototype.parsePacket = function parsePacket(header, data) {
   switch (header.cmd) {
+    case packets.types.ENV:
+      return packets.EnvPacket.fromRaw(data);
     case packets.types.EVENT:
       return packets.EventPacket.fromRaw(data);
     case packets.types.LOG:
diff --git a/lib/workers/worker-browser.js b/lib/workers/worker-browser.js
deleted file mode 100644
index b53af601..00000000
--- a/lib/workers/worker-browser.js
+++ /dev/null
@@ -1,20 +0,0 @@
-/*!
- * worker.js - worker thread/process for bcoin
- * Copyright (c) 2014-2015, Fedor Indutny (MIT License)
- * Copyright (c) 2014-2017, Christopher Jeffrey (MIT License).
- * https://github.com/bcoin-org/bcoin
- */
-
-'use strict';
-
-const Master = require('./master');
-
-self.onmessage = function onmessage(event) {
-  let env, server;
-
-  self.onmessage = function() {};
-
-  env = JSON.parse(event.data);
-  server = new Master();
-  server.listen(env);
-};
diff --git a/lib/workers/worker.js b/lib/workers/worker.js
index bce8c991..92fdc33f 100644
--- a/lib/workers/worker.js
+++ b/lib/workers/worker.js
@@ -10,4 +10,4 @@
 const Master = require('./master');
 const server = new Master();
 
-server.listen(process.env);
+server.listen();
diff --git a/lib/workers/workerpool.js b/lib/workers/workerpool.js
index c702586d..942d67fc 100644
--- a/lib/workers/workerpool.js
+++ b/lib/workers/workerpool.js
@@ -364,12 +364,7 @@ function Worker(file) {
   this.parser = new Parser();
   this.pending = new Map();
 
-  this.child = new Child(file, {
-    BCOIN_WORKER_NETWORK: Network.type,
-    BCOIN_WORKER_ISTTY: process.stdout
-      ? (process.stdout.isTTY ? '1' : '0')
-      : '0'
-  });
+  this.child = new Child(file);
 
   this.init();
 }
@@ -426,6 +421,13 @@ Worker.prototype.listen = function listen() {
       this.emit('error', e);
     }
   });
+
+  this.sendEnv({
+    BCOIN_WORKER_NETWORK: Network.type,
+    BCOIN_WORKER_ISTTY: process.stdout
+      ? (process.stdout.isTTY ? '1' : '0')
+      : '0'
+  });
 };
 
 /**
@@ -475,6 +477,16 @@ Worker.prototype.send = function send(packet) {
   return this.write(this.framer.packet(packet));
 };
 
+/**
+ * Send environment.
+ * @param {Object} env
+ * @returns {Boolean}
+ */
+
+Worker.prototype.sendEnv = function sendEnv(env) {
+  return this.send(new packets.EnvPacket(env));
+};
+
 /**
  * Emit an event on the worker side.
  * @param {String} event
diff --git a/webpack.browser.js b/webpack.browser.js
index 3229d794..d5bded28 100644
--- a/webpack.browser.js
+++ b/webpack.browser.js
@@ -10,7 +10,7 @@ module.exports = {
   target: 'web',
   entry: {
     'bcoin': './lib/bcoin-browser',
-    'bcoin-worker': './lib/workers/worker-browser'
+    'bcoin-worker': './lib/workers/worker'
   },
   output: {
     path: path.join(__dirname, 'browser'),
diff --git a/webpack.compat.js b/webpack.compat.js
index 424508c4..207aed8d 100644
--- a/webpack.compat.js
+++ b/webpack.compat.js
@@ -9,7 +9,7 @@ module.exports = {
   target: 'web',
   entry: {
     'bcoin': './lib/bcoin-browser',
-    'bcoin-worker': './lib/workers/worker-browser'
+    'bcoin-worker': './lib/workers/worker'
   },
   output: {
     path: path.join(__dirname, 'browser'),