diff --git a/lib/client.js b/lib/client.js
index ede3660..bf60932 100644
--- a/lib/client.js
+++ b/lib/client.js
@@ -11,7 +11,7 @@ Client.create = function() {
   var instance = Object.create(proto);
   constructor.apply(instance, arguments);
   return instance;
-}
+};
 
 /**
  * Constructor
@@ -24,7 +24,7 @@ function constructor(opts) {
   this.path = opts.path || '';
 
   underscore.bindAll.call(underscore, [this] + this._bound);
-};
+}
 
 /**
  * Specifies which methods are bound to the instance.
@@ -75,7 +75,7 @@ proto.request = function(method, resource, data, callback) {
     options.headers['Content-Length'] = data.length;
   }
 
-  req = http.request(options)
+  req = http.request(options);
   
   // Buffer up the response body and proceed.
   req.on('response', function(res) {
@@ -129,7 +129,7 @@ proto._requestDidComplete = function(res, body, callback) {
 
   // Automatically follow redirects.
   if (code >= 300 && code < 400) {
-    return this.get(res.headers['location'], callback);
+    return this.get(res.headers.location, callback);
   }
 
   if (!type.match('application/json')) {
@@ -161,7 +161,7 @@ proto._requestDidComplete = function(res, body, callback) {
 proto._requestDidFail = function(res, body, cb) {
   var type, data, error;
 
-  type = res.headers['content-type'] || ""
+  type = res.headers['content-type'] || "";
 
   // The content-type is expected to be text/plain.
   if (type !== 'text/plain') {
@@ -187,5 +187,9 @@ proto._requestDidFail = function(res, body, cb) {
     error = res.statusCode === 404 ? "Unknown command" : "Unknown error";
   }
 
+  if (typeof error === 'string') {
+    error = new Error(error);
+  }
+
   cb(error);
 };
diff --git a/lib/endpoint.js b/lib/endpoint.js
index f6e7b6b..f1fed0f 100644
--- a/lib/endpoint.js
+++ b/lib/endpoint.js
@@ -31,7 +31,7 @@ function constructor(opts) {
     , port: opts.port
     , path: opts.path
   });
-};
+}
 
 /**
  * Retrieves status of the endpoint.
@@ -43,7 +43,7 @@ proto.status = function(callback) {
     if (err) {
       return callback(err);
     }
-    
+
     callback(null, res.value);
   });
 };
diff --git a/lib/session.js b/lib/session.js
index af490da..0821be2 100644
--- a/lib/session.js
+++ b/lib/session.js
@@ -72,11 +72,14 @@ proto.execute = function(fn, args, callback) {
 
   if (typeof args === 'function') {
     callback = args;
-    args = [];
+    args     = null;
   }
+
+  args = args || [];
+
   this.post('/execute', {script: fn, args: args}, function(err, res) {
     if (err) {
-      callback(err);
+      return callback(err);
     }
 
     callback(null, res.value);
diff --git a/test/endpoint_test.js b/test/endpoint_test.js
index 2f60f65..de5ad1f 100644
--- a/test/endpoint_test.js
+++ b/test/endpoint_test.js
@@ -1,3 +1,5 @@
+/*global suite test*/
+
 var assert     = require('chai').assert
   , spy        = require('sinon').spy
   , Endpoint   = require('webdriver/lib/endpoint')
diff --git a/test/session_test.js b/test/session_test.js
index e59bb3c..22d17f8 100644
--- a/test/session_test.js
+++ b/test/session_test.js
@@ -1,3 +1,5 @@
+/*global suite test*/
+
 var assert  = require('chai').assert
    ,spy     = require('sinon').spy
   , Session = require('webdriver/lib/session');
@@ -32,6 +34,7 @@ suite('Session', function() {
       assert.instanceOf(session, Session);
     });
   }); // constructor
+
   suite('request', function() {
     var method   = 'GET'
       , resource = '/foo'
@@ -54,6 +57,7 @@ suite('Session', function() {
       assert.equal(args[3], callback,                    'callback is not modified');
     });
   }); // request
+
   suite('url', function() {
     test('retrieves url when called without string', function() {
       var client   = fakeClient()
@@ -71,6 +75,7 @@ suite('Session', function() {
       assert.equal(args[2], null,                        'params are not defined');
       assert.equal(args[3], callback,                    'callback is passed');
     });
+
     test('navigates to url when called with a string', function() {
       var client   = fakeClient()
         , session  = Session.create({id: 1, client: client})