diff --git a/lib/x11/xcore.js b/lib/x11/xcore.js
index b3c476d..9c0b9ac 100644
--- a/lib/x11/xcore.js
+++ b/lib/x11/xcore.js
@@ -19,10 +19,11 @@ var xerrors = require('./xerrors');
 var coreRequests = require('./corereqs');
 var stdatoms = require('./stdatoms');
 
-function XClient(stream, displayNum, screenNum)
+function XClient(stream, displayNum, screenNum, options)
 {
     EventEmitter.call(this);
     this.stream = stream;
+    this.options = options ? options : {};
 
     // TODO: this is probably not used
     this.core_requests = {};
@@ -123,17 +124,18 @@ XClient.prototype.importRequestsFromTemplates = function(target, reqs)
                client.seq_num = 0;
             else
                client.seq_num++;
-
+           
             // disable long stack trace for the moment, it's too expensive
             // performance when enabled (travis-ci worker, Xfvb): 70000 requests finished in 52196 ms, 1341.0989347842747 req/sec
             // without: 70000 requests finished in 14904 ms, 4696.725711218465 req/sec
             // MBPro, XQuartz: with 3600 req/sec, without 24200 req/sec 
-            /*
-            var err = new Error;
-            err.name = reqName;
-            Error.captureStackTrace(err, arguments.callee);
-            client.seq2stack[client.seq_num] = err.stack;
-            */
+            if (this.options.debug === true) {
+               var err = new Error();
+               err.name = reqName; //???
+               Error.captureStackTrace(err, arguments.callee);
+               err.timestamp = Date.now();
+               client.seq2stack[client.seq_num] = err;
+            }
 
             // is it fast?
             var args = Array.prototype.slice.call(req_proxy.arguments);
@@ -318,11 +320,12 @@ XClient.prototype.expectReplyHeader = function()
             if (type == 0)
             {              
                 var error_code = res[1];
-                var error = {};
+                var error = new Error();
                 error.error = error_code;
                 error.seq = seq_num;
                 error.message = xerrors.errorText[error_code];
-                error.stack = client.seq2stack[error.seq]
+                if (client.options.debug)
+                    error.stack = client.seq2stack[error.seq]
 
                 // unpack error packet (32 bytes for all error types, 8 of them in CCSL header)
                 client.pack_stream.get(24, function(buf) {
@@ -467,7 +470,7 @@ module.exports.createClient = function(initCb, display, options)
     {
     	stream = net.createConnection(6000 + parseInt(displayNum), host);
     }
-    var client = new XClient(stream, displayNum, screenNum);
+    var client = new XClient(stream, displayNum, screenNum, options);
     if (initCb)
     {
         client.on('connect', function(display) {
diff --git a/test/errors.js b/test/errors.js
new file mode 100644
index 0000000..4109396
--- /dev/null
+++ b/test/errors.js
@@ -0,0 +1,30 @@
+var x11 = require('../lib/x11');
+var should = require('should');
+var assert = require('assert');
+
+describe('Client', function() {
+
+  var display;
+  beforeEach(function(done) {
+      var client = x11.createClient(function(dpy) {
+      display=dpy;
+      done();
+    });
+  });
+
+  it('should emit error which is instance of Error with seqence number corresponding to source request', function(done) {
+    display.client.options.debug = true;
+    display.client.CreateWindow(); // should emit error
+    var seq = display.client.seq_num;
+    display.client.once('error', function(err) {
+        assert.equal(err.constructor, Error);
+        assert.equal(seq, err.seq);
+        display.client.CreateWindow(); // should emit error
+        seq = display.client.seq_num;
+        display.client.once('error', function(err) {
+            assert.equal(seq, err.seq);
+            done();
+        });
+     });
+  });
+});