diff --git a/src/Io/Sender.php b/src/Io/Sender.php
index 0894c574..acbb6e7d 100644
--- a/src/Io/Sender.php
+++ b/src/Io/Sender.php
@@ -94,8 +94,10 @@ public function send(RequestInterface $request)
         }
 
         // automatically add `Connection: close` request header for HTTP/1.1 requests to avoid connection reuse
-        if ($request->getProtocolVersion() === '1.1' && !$request->hasHeader('Connection')) {
+        if ($request->getProtocolVersion() === '1.1') {
             $request = $request->withHeader('Connection', 'close');
+        } else {
+            $request = $request->withoutHeader('Connection');
         }
 
         // automatically add `Authorization: Basic …` request header if URL includes `user:pass@host`
diff --git a/tests/Io/SenderTest.php b/tests/Io/SenderTest.php
index c2357a1a..4ef06442 100644
--- a/tests/Io/SenderTest.php
+++ b/tests/Io/SenderTest.php
@@ -302,6 +302,20 @@ public function getHttp10RequestShouldSendAGetRequestWithoutConnectionHeaderByDe
         $sender->send($request);
     }
 
+    /** @test */
+    public function getHttp10RequestShouldSendAGetRequestWithoutConnectionHeaderEvenWhenConnectionKeepAliveHeaderIsSpecified()
+    {
+        $client = $this->getMockBuilder('React\Http\Client\Client')->disableOriginalConstructor()->getMock();
+        $client->expects($this->once())->method('request')->with($this->callback(function (RequestInterface $request) {
+            return !$request->hasHeader('Connection');
+        }))->willReturn($this->getMockBuilder('React\Http\Io\ClientRequestStream')->disableOriginalConstructor()->getMock());
+
+        $sender = new Sender($client);
+
+        $request = new Request('GET', 'http://www.example.com', array('Connection' => 'keep-alive'), '', '1.0');
+        $sender->send($request);
+    }
+
     /** @test */
     public function getHttp11RequestShouldSendAGetRequestWithConnectionCloseHeaderByDefault()
     {
@@ -317,16 +331,16 @@ public function getHttp11RequestShouldSendAGetRequestWithConnectionCloseHeaderBy
     }
 
     /** @test */
-    public function getHttp11RequestShouldSendAGetRequestWithGivenConnectionUpgradeHeader()
+    public function getHttp11RequestShouldSendAGetRequestWithConnectionCloseHeaderEvenWhenConnectionKeepAliveHeaderIsSpecified()
     {
         $client = $this->getMockBuilder('React\Http\Client\Client')->disableOriginalConstructor()->getMock();
         $client->expects($this->once())->method('request')->with($this->callback(function (RequestInterface $request) {
-            return $request->getHeaderLine('Connection') === 'upgrade';
+            return $request->getHeaderLine('Connection') === 'close';
         }))->willReturn($this->getMockBuilder('React\Http\Io\ClientRequestStream')->disableOriginalConstructor()->getMock());
 
         $sender = new Sender($client);
 
-        $request = new Request('GET', 'http://www.example.com', array('Connection' => 'upgrade'), '', '1.1');
+        $request = new Request('GET', 'http://www.example.com', array('Connection' => 'keep-alive'), '', '1.1');
         $sender->send($request);
     }