diff --git a/CHANGELOG.md b/CHANGELOG.md
index 1a7d586..d803fbe 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,9 @@
 # Change Log
 
+### Added
+
+- Support for `php-http/httplug` version 2.0, hence supporting PSR-18 
+
 ## 1.5.0 - 2018-xx-xx
 
 ### Added
diff --git a/composer.json b/composer.json
index 028f1bb..97141f3 100644
--- a/composer.json
+++ b/composer.json
@@ -14,7 +14,7 @@
         "php": "^5.5 || ^7.0"
     },
     "require-dev": {
-        "php-http/httplug": "^1.0",
+        "php-http/httplug": "^1.0|^2.0",
         "php-http/message-factory": "^1.0",
         "puli/composer-plugin": "1.0.0-beta10",
         "phpspec/phpspec": "^2.4",
diff --git a/spec/HttpClientDiscoverySpec.php b/spec/HttpClientDiscoverySpec.php
index c9f9809..a5d4259 100644
--- a/spec/HttpClientDiscoverySpec.php
+++ b/spec/HttpClientDiscoverySpec.php
@@ -12,6 +12,9 @@
 use Puli\Repository\Api\ResourceRepository;
 use PhpSpec\ObjectBehavior;
 use spec\Http\Discovery\Helper\DiscoveryHelper;
+use Http\Discovery\HttpClientDiscovery;
+use spec\Http\Discovery\Stub\HttpClientStub;
+use spec\Http\Discovery\Stub\PSR18ClientStub;
 
 class HttpClientDiscoverySpec extends ObjectBehavior
 {
@@ -23,23 +26,38 @@ function let()
 
     function it_is_initializable()
     {
-        $this->shouldHaveType('Http\Discovery\HttpClientDiscovery');
+        $this->shouldHaveType(HttpClientDiscovery::class);
     }
 
     function it_is_a_class_discovery()
     {
-        $this->shouldHaveType('Http\Discovery\ClassDiscovery');
+        $this->shouldHaveType(ClassDiscovery::class);
     }
 
-    function it_finds_a_http_client(DiscoveryStrategy $strategy) {
+    function it_finds_a_http_client(DiscoveryStrategy $strategy) 
+    {
+        $candidate = ['class' => HttpClientStub::class, 'condition' => true];
+        if ($this->psr18IsInUse()) {
+            $candidate['class'] = PSR18ClientStub::class;
+        }
 
-        $candidate = ['class' => 'spec\Http\Discovery\Stub\HttpClientStub', 'condition' => true];
         DiscoveryHelper::setClasses(HttpClient::class, [$candidate]);
 
-        $this->find()->shouldImplement('Http\Client\HttpClient');
+        $this->find()->shouldImplement(HttpClient::class);
     }
 
     function it_throw_exception(DiscoveryStrategy $strategy) {
         $this->shouldThrow(NotFoundException::class)->duringFind();
     }
+
+    private function psr18IsInUse()
+    {
+        if (PHP_MAJOR_VERSION < 7) {
+            return false;
+        }
+
+        $reflection = new \ReflectionMethod(HttpClient::class, 'sendRequest');
+        
+        return $reflection->hasReturnType();
+    }
 }
diff --git a/spec/Stub/PSR18ClientStub.php b/spec/Stub/PSR18ClientStub.php
new file mode 100644
index 0000000..cf3aa0c
--- /dev/null
+++ b/spec/Stub/PSR18ClientStub.php
@@ -0,0 +1,14 @@
+<?php
+
+namespace spec\Http\Discovery\Stub;
+
+use Http\Client\HttpClient;
+use Psr\Http\Message\RequestInterface;
+use Psr\Http\Message\ResponseInterface;
+
+class PSR18ClientStub implements HttpClient
+{
+    public function sendRequest(RequestInterface $request): ResponseInterface
+    {
+    }
+}