diff --git a/lib/utils/util.js b/lib/utils/util.js
index c257f5b2..2109aa7e 100644
--- a/lib/utils/util.js
+++ b/lib/utils/util.js
@@ -416,9 +416,8 @@ util.fmt = nodeUtil.format;
  */
 
 util.format = function format(args, color) {
-  color = color
-    ? (process.stdout ? process.stdout.isTTY : false)
-    : false;
+  if (color == null)
+    color = process.stdout ? process.stdout.isTTY : false;
 
   return typeof args[0] === 'object'
     ? util.inspectify(args[0], color)
@@ -446,7 +445,7 @@ util.log = function log() {
     return;
   }
 
-  msg = util.format(args, true);
+  msg = util.format(args);
   process.stdout.write(msg + '\n');
 };
 
@@ -471,7 +470,7 @@ util.error = function error() {
     return;
   }
 
-  msg = util.format(args, true);
+  msg = util.format(args);
   process.stderr.write(msg + '\n');
 };
 
diff --git a/lib/workers/master.js b/lib/workers/master.js
index a6f7f60a..c97cc7ff 100644
--- a/lib/workers/master.js
+++ b/lib/workers/master.js
@@ -34,6 +34,7 @@ function Master() {
   this.parser = new Parser();
   this.env = {};
   this.listening = false;
+  this.color = false;
 
   this._init();
 }
@@ -184,12 +185,14 @@ Master.prototype.destroy = function destroy() {
 
 Master.prototype.log = function log() {
   var items = new Array(arguments.length);
-  var i;
+  var i, text;
 
   for (i = 0; i < items.length; i++)
     items[i] = arguments[i];
 
-  this.send(new packets.LogPacket(items));
+  text = util.format(items, this.color);
+
+  this.send(new packets.LogPacket(text));
 };
 
 /**
@@ -205,6 +208,7 @@ Master.prototype.listen = function listen(env) {
 
   this.env = env;
   this.listening = true;
+  this.color = +env.BCOIN_WORKER_ISTTY === 1;
 
   Network.set(env.BCOIN_WORKER_NETWORK);
 
diff --git a/lib/workers/packets.js b/lib/workers/packets.js
index b478a3a4..f2a20074 100644
--- a/lib/workers/packets.js
+++ b/lib/workers/packets.js
@@ -87,9 +87,9 @@ EventPacket.fromRaw = function fromRaw(data) {
  * @constructor
  */
 
-function LogPacket(items) {
+function LogPacket(text) {
   Packet.call(this);
-  this.items = items || [];
+  this.text = text || '';
 }
 
 util.inherits(LogPacket, Packet);
@@ -97,13 +97,13 @@ util.inherits(LogPacket, Packet);
 LogPacket.prototype.cmd = packetTypes.LOG;
 
 LogPacket.prototype.toRaw = function toRaw(bw) {
-  bw.writeVarString(JSON.stringify(this.items), 'utf8');
+  bw.writeVarString(this.text, 'utf8');
 };
 
 LogPacket.fromRaw = function fromRaw(data) {
   var br = new BufferReader(data, true);
   var packet = new LogPacket();
-  packet.items = JSON.parse(br.readVarString('utf8'));
+  packet.text = br.readVarString('utf8');
   return packet;
 };
 
diff --git a/lib/workers/workerpool.js b/lib/workers/workerpool.js
index 00e3008c..2ccf512d 100644
--- a/lib/workers/workerpool.js
+++ b/lib/workers/workerpool.js
@@ -411,7 +411,10 @@ function Worker(id) {
   this.child = null;
   this.pending = {};
   this.env = {
-    BCOIN_WORKER_NETWORK: Network.type
+    BCOIN_WORKER_NETWORK: Network.type,
+    BCOIN_WORKER_ISTTY: process.stdout
+      ? (process.stdout.isTTY ? '1' : '0')
+      : '0'
   };
 
   this._init();
@@ -581,7 +584,7 @@ Worker.prototype.handlePacket = function handlePacket(packet) {
       break;
     case packets.types.LOG:
       util.log('Worker %d:', this.id);
-      util.log.apply(util, packet.items);
+      util.log(packet.text);
       break;
     case packets.types.ERROR:
       this.emit('error', packet.error);
@@ -680,7 +683,7 @@ Worker.prototype.execute = function execute(packet, timeout) {
 Worker.prototype._execute = function _execute(packet, timeout, callback) {
   var job = new PendingJob(this, packet.id, callback);
 
-  assert(!this.pending[packet.id]);
+  assert(!this.pending[packet.id], 'ID overflow.');
 
   this.pending[packet.id] = job;
 
@@ -697,7 +700,10 @@ Worker.prototype._execute = function _execute(packet, timeout, callback) {
 
 Worker.prototype.resolveJob = function resolveJob(id, result) {
   var job = this.pending[id];
-  assert(job);
+
+  if (!job)
+    throw new Error('Job ' + id + ' is not in progress.');
+
   job.finish(null, result);
 };
 
@@ -709,7 +715,10 @@ Worker.prototype.resolveJob = function resolveJob(id, result) {
 
 Worker.prototype.rejectJob = function rejectJob(id, err) {
   var job = this.pending[id];
-  assert(job);
+
+  if (!job)
+    throw new Error('Job ' + id + ' is not in progress.');
+
   job.finish(err);
 };
 
@@ -751,7 +760,7 @@ function PendingJob(worker, id, callback) {
 PendingJob.prototype.start = function start(timeout) {
   var self = this;
 
-  if (timeout === -1)
+  if (!timeout || timeout === -1)
     return;
 
   this.timer = setTimeout(function() {