diff --git a/lib/workers/master.js b/lib/workers/master.js
index 6bf3785b..0c6c9545 100644
--- a/lib/workers/master.js
+++ b/lib/workers/master.js
@@ -83,13 +83,14 @@ Master.prototype._initWebWorkers = function _initWebWorkers() {
 
   global.onmessage = (event) => {
     let data;
-    if (typeof event.data !== 'string') {
+    if (typeof event.data === 'string') {
+      data = Buffer.from(event.data, 'hex');
+      assert(data.length === event.data.length / 2);
+    } else {
       assert(event.data && typeof event.data === 'object');
-      assert(event.data.data);
+      assert(event.data.data && typeof event.data.data.length === 'number');
       data = event.data.data;
       data.__proto__ = Buffer.prototype;
-    } else {
-      data = Buffer.from(event.data, 'hex');
     }
     this.emit('data', data);
   };
@@ -112,7 +113,7 @@ Master.prototype._initChildProcess = function _initChildProcess() {
 
   process.on('uncaughtException', (err) => {
     this.send(new packets.ErrorPacket(err));
-    setTimeout(() => process.exit(1), 500);
+    setTimeout(() => process.exit(1), 1000);
   });
 };
 
diff --git a/lib/workers/workerpool.js b/lib/workers/workerpool.js
index 86e5b2eb..10d74745 100644
--- a/lib/workers/workerpool.js
+++ b/lib/workers/workerpool.js
@@ -176,7 +176,7 @@ WorkerPool.prototype.close = async function close() {
  */
 
 WorkerPool.prototype.spawn = function spawn(id) {
-  let child = new Worker(id);
+  let child = new Worker(id, this.masterURL);
 
   child.on('error', (err) => {
     this.emit('error', err, child);
@@ -416,24 +416,25 @@ WorkerPool.prototype.scrypt = async function scrypt(passwd, salt, N, r, p, len)
  * Represents a worker.
  * @alias module:workers.Worker
  * @constructor
- * @param {Number?} id
+ * @param {Number} id
+ * @param {String} masterURL
  */
 
-function Worker(id) {
+function Worker(id, masterURL) {
   if (!(this instanceof Worker))
-    return new Worker(id);
+    return new Worker(id, masterURL);
 
   EventEmitter.call(this);
 
   this.framer = new Framer();
   this.parser = new Parser();
 
-  this.id = id != null ? id : -1;
+  this.id = id;
   this.child = null;
   this.pending = new Map();
 
   this.env = {
-    BCOIN_MASTER_URL: this.masterURL,
+    BCOIN_MASTER_URL: masterURL,
     BCOIN_WORKER_NETWORK: Network.type,
     BCOIN_WORKER_ISTTY: process.stdout
       ? (process.stdout.isTTY ? '1' : '0')
@@ -491,13 +492,14 @@ Worker.prototype._initWebWorkers = function _initWebWorkers() {
 
   this.child.onmessage = (event) => {
     let data;
-    if (typeof event.data !== 'string') {
+    if (typeof event.data === 'string') {
+      data = Buffer.from(event.data, 'hex');
+      assert(data.length === event.data.length / 2);
+    } else {
       assert(event.data && typeof event.data === 'object');
-      assert(event.data.data);
+      assert(event.data.data && typeof event.data.data.length === 'number');
       data = event.data.data;
       data.__proto__ = Buffer.prototype;
-    } else {
-      data = Buffer.from(event.data, 'hex');
     }
     this.emit('data', data);
   };