diff --git a/src/Client.php b/src/Client.php
index 456564c..677a00f 100644
--- a/src/Client.php
+++ b/src/Client.php
@@ -15,9 +15,9 @@ public function __construct(ConnectorInterface $connector, ConnectorInterface $s
         $this->secureConnector = $secureConnector;
     }
 
-    public function request($method, $url, array $headers = [])
+    public function request($method, $url, array $headers = [], $protocolVersion = '1.0')
     {
-        $requestData = new RequestData($method, $url, $headers);
+        $requestData = new RequestData($method, $url, $headers, $protocolVersion);
         $connector = $this->getConnectorForScheme($requestData->getScheme());
 
         return new Request($connector, $requestData);
diff --git a/src/RequestData.php b/src/RequestData.php
index 2d379aa..961db22 100644
--- a/src/RequestData.php
+++ b/src/RequestData.php
@@ -7,14 +7,14 @@ class RequestData
     private $method;
     private $url;
     private $headers;
+    private $protocolVersion;
 
-    private $protocolVersion = '1.0';
-
-    public function __construct($method, $url, array $headers = [])
+    public function __construct($method, $url, array $headers = [], $protocolVersion = '1.0')
     {
         $this->method = $method;
         $this->url = $url;
         $this->headers = $headers;
+        $this->protocolVersion = $protocolVersion;
     }
 
     private function mergeDefaultheaders(array $headers)
diff --git a/tests/RequestDataTest.php b/tests/RequestDataTest.php
index 7fbeb55..6fc8f15 100644
--- a/tests/RequestDataTest.php
+++ b/tests/RequestDataTest.php
@@ -34,6 +34,20 @@ public function toStringReturnsHTTPRequestMessageWithProtocolVersion()
         $this->assertSame($expected, $requestData->__toString());
     }
 
+    /** @test */
+    public function toStringReturnsHTTPRequestMessageWithProtocolVersionThroughConstructor()
+    {
+        $requestData = new RequestData('GET', 'http://www.example.com', [], '1.1');
+
+        $expected = "GET / HTTP/1.1\r\n" .
+            "Host: www.example.com\r\n" .
+            "User-Agent: React/alpha\r\n" .
+            "Connection: close\r\n" .
+            "\r\n";
+
+        $this->assertSame($expected, $requestData->__toString());
+    }
+
     /** @test */
     public function toStringUsesUserPassFromURL()
     {