diff --git a/composer.json b/composer.json
index d55ab33..5a210a2 100644
--- a/composer.json
+++ b/composer.json
@@ -24,7 +24,8 @@
     },
     "require-dev": {
         "roave/security-advisories": "dev-master",
-        "phpunit/phpunit": "^7.0"
+        "phpunit/phpunit": "^7.0",
+        "guzzlehttp/guzzle": "^6.3"
     },
     "suggest": {
         "csa/guzzle-bundle": "Allow to unseal and verify response from sapient api automatically."
diff --git a/src/DependencyInjection/Configuration.php b/src/DependencyInjection/Configuration.php
index 948a66a..9e48bcf 100644
--- a/src/DependencyInjection/Configuration.php
+++ b/src/DependencyInjection/Configuration.php
@@ -33,6 +33,7 @@ public function getConfigTreeBuilder()
                     ->children()
                         ->booleanNode('unseal')->defaultFalse()->end()
                         ->booleanNode('verify')->defaultFalse()->end()
+                        ->scalarNode('requester_name')->defaultFalse()->end()
                     ->end()
                 ->end()
                 ->arrayNode('sealing_public_keys')
diff --git a/src/DependencyInjection/SapientExtension.php b/src/DependencyInjection/SapientExtension.php
index ce182b5..1877e18 100644
--- a/src/DependencyInjection/SapientExtension.php
+++ b/src/DependencyInjection/SapientExtension.php
@@ -45,6 +45,11 @@ public function load(array $configs, ContainerBuilder $container)
             if ($config['guzzle_middleware']['unseal']) {
                 $loader->load('guzzle_middleware/unseal_response.yml');
             }
+
+            if ($config['guzzle_middleware']['requester_name']) {
+                $container->setParameter('sapient.guzzle_middleware.requester_name', $config['guzzle_middleware']['requester_name']);
+                $loader->load('guzzle_middleware/requester_header.yml');
+            }
         }
     }
 }
diff --git a/src/GuzzleHttp/Middleware/RequesterHeaderMiddleware.php b/src/GuzzleHttp/Middleware/RequesterHeaderMiddleware.php
new file mode 100644
index 0000000..30b3f74
--- /dev/null
+++ b/src/GuzzleHttp/Middleware/RequesterHeaderMiddleware.php
@@ -0,0 +1,33 @@
+<?php
+declare(strict_types=1);
+
+namespace lepiaf\SapientBundle\GuzzleHttp\Middleware;
+
+use lepiaf\SapientBundle\Service\PublicKeyGetter;
+use Psr\Http\Message\RequestInterface;
+
+class RequesterHeaderMiddleware
+{
+    /**
+     * @var string
+     */
+    private $requesterName;
+
+    /**
+     * @param string $requesterName
+     */
+    public function __construct(string $requesterName)
+    {
+        $this->requesterName = $requesterName;
+    }
+
+    public function __invoke(callable $handler): callable
+    {
+        return function(RequestInterface $request, array $options) use ($handler) {
+            return $handler(
+                $request->withHeader(PublicKeyGetter::HEADER_REQUESTER, $this->requesterName),
+                $options
+            );
+        };
+    }
+}
diff --git a/src/Resources/config/guzzle_middleware/requester_header.yml b/src/Resources/config/guzzle_middleware/requester_header.yml
new file mode 100644
index 0000000..7f775f2
--- /dev/null
+++ b/src/Resources/config/guzzle_middleware/requester_header.yml
@@ -0,0 +1,6 @@
+services:
+  lepiaf\SapientBundle\GuzzleHttp\Middleware\RequesterHeaderMiddleware:
+    arguments:
+      - '%sapient.guzzle_middleware.requester_name%'
+    tags:
+      - { name: 'csa_guzzle.middleware', alias: 'requester_name' }
diff --git a/src/Resources/doc/reference.rst b/src/Resources/doc/reference.rst
index 25c1cf8..984d162 100644
--- a/src/Resources/doc/reference.rst
+++ b/src/Resources/doc/reference.rst
@@ -16,6 +16,7 @@ Reference
         guzzle_middleware:
             unseal: boolean
             verify: boolean
+            requester_name: string
         sealing_public_keys:
             -
                 name: string
@@ -104,6 +105,16 @@ If enable, it will activate Guzzle middleware that verify signature in response.
 
 Before enabling this option, you must configure verifying_public_keys_ array.
 
+.. guzzle_middleware.requester_name:
+guzzle_middleware.requester_name
+------------------------
+
+This Guzzle middleware will add a header ``Sapient-Requester`` automatically on each request. This
+header is used by recipient to choose the right key to encrypt response.
+
+It is optional but highly recommended. If not enable, you must add header manually in
+Guzzle client configuration.
+
 .. sealing_public_keys:
 sealing_public_keys
 -------------------
diff --git a/src/Service/PublicKeyGetter.php b/src/Service/PublicKeyGetter.php
index 4bee0be..53d05f5 100644
--- a/src/Service/PublicKeyGetter.php
+++ b/src/Service/PublicKeyGetter.php
@@ -14,7 +14,7 @@
 class PublicKeyGetter
 {
     public const HEADER_SIGNER = 'Sapient-Signer';
-    private const HEADER_REQUESTER = 'Sapient-Requester';
+    public const HEADER_REQUESTER = 'Sapient-Requester';
 
     /**
      * @var array
diff --git a/tests/GuzzleHttp/Middleware/RequesterHeaderMiddlewareTest.php b/tests/GuzzleHttp/Middleware/RequesterHeaderMiddlewareTest.php
new file mode 100644
index 0000000..1ba76f9
--- /dev/null
+++ b/tests/GuzzleHttp/Middleware/RequesterHeaderMiddlewareTest.php
@@ -0,0 +1,31 @@
+<?php
+
+namespace Tests\lepiaf\SapientBundle\EventSubscriber;
+
+use GuzzleHttp\Client;
+use GuzzleHttp\Handler\MockHandler;
+use GuzzleHttp\HandlerStack;
+use GuzzleHttp\Psr7\Response;
+use lepiaf\SapientBundle\GuzzleHttp\Middleware\RequesterHeaderMiddleware;
+use PHPUnit\Framework\TestCase;
+use Psr\Http\Message\RequestInterface;
+
+class RequesterHeaderMiddlewareTest extends TestCase
+{
+    public function testRequestWithHeader()
+    {
+        $mockHandler = new MockHandler([
+            function (RequestInterface $request) {
+                $this->assertTrue($request->hasHeader('Sapient-Requester'));
+                $this->assertSame(['client-bob'], $request->getHeader('Sapient-Requester'));
+
+                return new Response(200);
+            },
+        ]);
+        $handler = HandlerStack::create($mockHandler);
+        $handler->push(new RequesterHeaderMiddleware('client-bob'));
+        $client = new Client(['handler' => $handler]);
+
+        $client->request('GET', 'http://api.example.com/api/ping');
+    }
+}