diff --git a/CHANGELOG.md b/CHANGELOG.md
index c42d9c1..ea10080 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,10 @@
 - Add a flexible http client providing both contract, and only emulating what's necessary
 - HTTP Client Router: route requests to underlying clients
 
+### Deprecated
+
+- Extending client classes, they will be made final in version 2.0
+
 
 ## 1.0.0 - 2016-01-27
 
diff --git a/spec/FlexibleHttpClientSpec.php b/spec/FlexibleHttpClientSpec.php
index 3396572..0df9e1e 100644
--- a/spec/FlexibleHttpClientSpec.php
+++ b/spec/FlexibleHttpClientSpec.php
@@ -2,16 +2,12 @@
 
 namespace spec\Http\Client\Common;
 
-use Http\Client\Common\HttpAsyncClientDecorator;
-use Http\Client\Common\HttpClientDecorator;
-use Http\Client\Common\FlexibleHttpClient;
 use Http\Client\HttpAsyncClient;
 use Http\Client\HttpClient;
 use Http\Promise\Promise;
 use Psr\Http\Message\RequestInterface;
 use Psr\Http\Message\ResponseInterface;
 use PhpSpec\ObjectBehavior;
-use Prophecy\Prophet;
 
 class FlexibleHttpClientSpec extends ObjectBehavior
 {
@@ -79,8 +75,10 @@ function it_emulates_a_client(
         $this->sendRequest($syncRequest)->shouldReturn($syncResponse);
     }
 
-    function it_does_not_emulate_a_client(FlexibleHttpClient $client, RequestInterface $syncRequest, RequestInterface $asyncRequest)
+    function it_does_not_emulate_a_client($client, RequestInterface $syncRequest, RequestInterface $asyncRequest)
     {
+        $client->implement('Http\Client\HttpClient');
+        $client->implement('Http\Client\HttpAsyncClient');
         $client->sendRequest($syncRequest)->shouldBeCalled();
         $client->sendRequest($asyncRequest)->shouldNotBeCalled();
         $client->sendAsyncRequest($asyncRequest)->shouldBeCalled();
diff --git a/src/FlexibleHttpClient.php b/src/FlexibleHttpClient.php
index 1fdad7f..58f8813 100644
--- a/src/FlexibleHttpClient.php
+++ b/src/FlexibleHttpClient.php
@@ -11,7 +11,7 @@
  *
  * @author Joel Wurtz <joel.wurtz@gmail.com>
  */
-class FlexibleHttpClient implements HttpClient, HttpAsyncClient
+final class FlexibleHttpClient implements HttpClient, HttpAsyncClient
 {
     use HttpClientDecorator;
     use HttpAsyncClientDecorator;