diff --git a/src/CacheInvalidator.php b/src/CacheInvalidator.php
index 54ef4b6d..1810f1e7 100644
--- a/src/CacheInvalidator.php
+++ b/src/CacheInvalidator.php
@@ -49,17 +49,17 @@ class CacheInvalidator
     /**
      * @var ProxyClientInterface
      */
-    protected $cache;
+    private $cache;
 
     /**
      * @var EventDispatcherInterface
      */
-    protected $eventDispatcher;
+    private $eventDispatcher;
 
     /**
      * @var string
      */
-    protected $tagsHeader = 'X-Cache-Tags';
+    private $tagsHeader = 'X-Cache-Tags';
 
     /**
      * Constructor
diff --git a/src/Event.php b/src/Event.php
index 1252d667..633af04f 100644
--- a/src/Event.php
+++ b/src/Event.php
@@ -15,7 +15,7 @@
 
 class Event extends BaseEvent
 {
-    protected $exception;
+    private $exception;
 
     /**
      * Set exception
diff --git a/src/EventListener/LogSubscriber.php b/src/EventListener/LogSubscriber.php
index 2eb1f658..28a40535 100644
--- a/src/EventListener/LogSubscriber.php
+++ b/src/EventListener/LogSubscriber.php
@@ -22,7 +22,7 @@ class LogSubscriber implements EventSubscriberInterface
     /**
      * @var LoggerInterface
      */
-    protected $logger;
+    private $logger;
 
     public function __construct(LoggerInterface $logger)
     {
@@ -50,7 +50,7 @@ public function onProxyResponseError(Event $event)
         $this->log(LogLevel::CRITICAL, $event->getException());
     }
 
-    protected function log($level, \Exception $exception)
+    private function log($level, \Exception $exception)
     {
         $context = array(
             'exception' => $exception
diff --git a/src/Exception/ExceptionCollection.php b/src/Exception/ExceptionCollection.php
index 74e90af3..44bb313b 100644
--- a/src/Exception/ExceptionCollection.php
+++ b/src/Exception/ExceptionCollection.php
@@ -17,7 +17,7 @@
  */
 class ExceptionCollection extends \Exception implements \IteratorAggregate, \Countable,  HttpCacheExceptionInterface
 {
-    protected $exceptions = array();
+    private $exceptions = array();
 
     /**
      * Add an exception to the collection
diff --git a/src/ProxyClient/AbstractProxyClient.php b/src/ProxyClient/AbstractProxyClient.php
index f7d019ad..42f836d6 100644
--- a/src/ProxyClient/AbstractProxyClient.php
+++ b/src/ProxyClient/AbstractProxyClient.php
@@ -34,21 +34,21 @@ abstract class AbstractProxyClient implements ProxyClientInterface
      *
      * @var array
      */
-    protected $servers;
+    private $servers;
 
     /**
      * HTTP client
      *
      * @var ClientInterface
      */
-    protected $client;
+    private $client;
 
     /**
      * Request queue
      *
      * @var array|RequestInterface[]
      */
-    protected $queue;
+    private $queue;
 
     /**
      * Constructor
@@ -156,7 +156,7 @@ protected function createRequest($method, $url, array $headers = array())
      *
      * @throws ExceptionCollection
      */
-    protected function sendRequests(array $requests)
+    private function sendRequests(array $requests)
     {
         $allRequests = array();
 
diff --git a/src/ProxyClient/Nginx.php b/src/ProxyClient/Nginx.php
index cbc1edf1..10d37c10 100644
--- a/src/ProxyClient/Nginx.php
+++ b/src/ProxyClient/Nginx.php
@@ -32,7 +32,7 @@ class Nginx extends AbstractProxyClient implements PurgeInterface, RefreshInterf
      *
      * @var string|false
      */
-    protected $purgeLocation;
+    private $purgeLocation;
 
     /**
      * {@inheritdoc}
diff --git a/src/ProxyClient/Varnish.php b/src/ProxyClient/Varnish.php
index ccba2d6d..1fdca451 100644
--- a/src/ProxyClient/Varnish.php
+++ b/src/ProxyClient/Varnish.php
@@ -37,7 +37,7 @@ class Varnish extends AbstractProxyClient implements BanInterface, PurgeInterfac
      *
      * @var array
      */
-    protected $defaultBanHeaders = array(
+    private $defaultBanHeaders = array(
         self::HTTP_HEADER_HOST         => self::REGEX_MATCH_ALL,
         self::HTTP_HEADER_URL          => self::REGEX_MATCH_ALL,
         self::HTTP_HEADER_CONTENT_TYPE => self::REGEX_MATCH_ALL