diff --git a/.travis.yml b/.travis.yml
index 968ece7d4..fbda89be8 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,8 +1,6 @@
 sudo: false
 language: node_js
 node_js:
-  - "4"
-  - "6"
   - "8"
   - "9"
 git:
diff --git a/lib/server.js b/lib/server.js
index df4058ea5..2d9a45c7a 100644
--- a/lib/server.js
+++ b/lib/server.js
@@ -148,6 +148,7 @@ Server.prototype.verify = function (req, upgrade, fn) {
   var isOriginInvalid = checkInvalidHeaderChar(req.headers.origin);
   if (isOriginInvalid) {
     req.headers.origin = null;
+    debug('origin header invalid');
     return fn(Server.errors.BAD_REQUEST, false);
   }
 
@@ -155,6 +156,7 @@ Server.prototype.verify = function (req, upgrade, fn) {
   var sid = req._query.sid;
   if (sid) {
     if (!this.clients.hasOwnProperty(sid)) {
+      debug('unknown sid "%s"', sid);
       return fn(Server.errors.UNKNOWN_SID, false);
     }
     if (!upgrade && this.clients[sid].transport.name !== transport) {
@@ -309,6 +311,7 @@ Server.prototype.handshake = function (transportName, req) {
       transport.supportsBinary = true;
     }
   } catch (e) {
+    debug('error handshaking to transport "%s"', transportName);
     sendErrorMessage(req, req.res, Server.errors.BAD_REQUEST);
     return;
   }
@@ -552,23 +555,33 @@ function checkInvalidHeaderChar(val) {
   val += '';
   if (val.length < 1)
     return false;
-  if (!validHdrChars[val.charCodeAt(0)])
+  if (!validHdrChars[val.charCodeAt(0)]) {
+    debug('invalid header, index 0, char "%s"', val.charCodeAt(0));
     return true;
+  }
   if (val.length < 2)
     return false;
-  if (!validHdrChars[val.charCodeAt(1)])
+  if (!validHdrChars[val.charCodeAt(1)]) {
+    debug('invalid header, index 1, char "%s"', val.charCodeAt(1));
     return true;
+  }
   if (val.length < 3)
     return false;
-  if (!validHdrChars[val.charCodeAt(2)])
+  if (!validHdrChars[val.charCodeAt(2)]) {
+    debug('invalid header, index 2, char "%s"', val.charCodeAt(2));
     return true;
+  }
   if (val.length < 4)
     return false;
-  if (!validHdrChars[val.charCodeAt(3)])
+  if (!validHdrChars[val.charCodeAt(3)]) {
+    debug('invalid header, index 3, char "%s"', val.charCodeAt(3));
     return true;
+  }
   for (var i = 4; i < val.length; ++i) {
-    if (!validHdrChars[val.charCodeAt(i)])
+    if (!validHdrChars[val.charCodeAt(i)]) {
+      debug('invalid header, index "%i", char "%s"', i, val.charCodeAt(i));
       return true;
+    }
   }
   return false;
 }
diff --git a/package.json b/package.json
index caac4c850..d99b2c31b 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "engine.io",
-  "version": "3.3.2",
+  "version": "3.4.0",
   "description": "The realtime engine behind Socket.IO. Provides the foundation of a bidirectional connection between client and server",
   "main": "lib/engine.io",
   "author": "Guillermo Rauch <guillermo@learnboost.com>",
@@ -26,16 +26,16 @@
   "license": "MIT",
   "dependencies": {
     "accepts": "~1.3.4",
-    "base64id": "1.0.0",
-    "debug": "~3.1.0",
-    "engine.io-parser": "~2.1.0",
-    "ws": "~6.1.0",
-    "cookie": "0.3.1"
+    "base64id": "2.0.0",
+    "cookie": "0.3.1",
+    "debug": "~4.1.0",
+    "engine.io-parser": "~2.2.0",
+    "ws": "^7.1.2"
   },
   "devDependencies": {
     "babel-eslint": "^8.0.2",
     "babel-preset-es2015": "^6.24.0",
-    "engine.io-client": "3.3.1",
+    "engine.io-client": "3.4.0",
     "eslint": "^4.5.0",
     "eslint-config-standard": "^10.2.1",
     "eslint-plugin-import": "^2.7.0",
diff --git a/test/engine.io.js b/test/engine.io.js
index c29d3934c..9387094c9 100644
--- a/test/engine.io.js
+++ b/test/engine.io.js
@@ -19,7 +19,7 @@ describe('engine', function () {
     expect(eio.protocol).to.be.a('number');
   });
 
-  it.skip('should be the same version as client', function () {
+  it('should be the same version as client', function () {
     var version = require('../package').version;
     expect(version).to.be(require('engine.io-client/package').version);
   });