diff --git a/src/Io/ClientRequestState.php b/src/Io/ClientRequestState.php
new file mode 100644
index 00000000..73a63a14
--- /dev/null
+++ b/src/Io/ClientRequestState.php
@@ -0,0 +1,16 @@
+<?php
+
+namespace React\Http\Io;
+
+/** @internal */
+class ClientRequestState
+{
+    /** @var int */
+    public $numRequests = 0;
+
+    /** @var ?\React\Promise\PromiseInterface */
+    public $pending = null;
+
+    /** @var ?\React\EventLoop\TimerInterface */
+    public $timeout = null;
+}
diff --git a/src/Io/Transaction.php b/src/Io/Transaction.php
index 7bf7008f..330ffed0 100644
--- a/src/Io/Transaction.php
+++ b/src/Io/Transaction.php
@@ -67,32 +67,31 @@ public function withOptions(array $options)
 
     public function send(RequestInterface $request)
     {
-        $deferred = new Deferred(function () use (&$deferred) {
-            if (isset($deferred->pending)) {
-                $deferred->pending->cancel();
-                unset($deferred->pending);
+        $state = new ClientRequestState();
+        $deferred = new Deferred(function () use ($state) {
+            if ($state->pending !== null) {
+                $state->pending->cancel();
+                $state->pending = null;
             }
         });
 
-        $deferred->numRequests = 0;
-
         // use timeout from options or default to PHP's default_socket_timeout (60)
         $timeout = (float)($this->timeout !== null ? $this->timeout : ini_get("default_socket_timeout"));
 
         $loop = $this->loop;
-        $this->next($request, $deferred)->then(
-            function (ResponseInterface $response) use ($deferred, $loop, &$timeout) {
-                if (isset($deferred->timeout)) {
-                    $loop->cancelTimer($deferred->timeout);
-                    unset($deferred->timeout);
+        $this->next($request, $deferred, $state)->then(
+            function (ResponseInterface $response) use ($state, $deferred, $loop, &$timeout) {
+                if ($state->timeout !== null) {
+                    $loop->cancelTimer($state->timeout);
+                    $state->timeout = null;
                 }
                 $timeout = -1;
                 $deferred->resolve($response);
             },
-            function ($e) use ($deferred, $loop, &$timeout) {
-                if (isset($deferred->timeout)) {
-                    $loop->cancelTimer($deferred->timeout);
-                    unset($deferred->timeout);
+            function ($e) use ($state, $deferred, $loop, &$timeout) {
+                if ($state->timeout !== null) {
+                    $loop->cancelTimer($state->timeout);
+                    $state->timeout = null;
                 }
                 $timeout = -1;
                 $deferred->reject($e);
@@ -106,13 +105,13 @@ function ($e) use ($deferred, $loop, &$timeout) {
         $body = $request->getBody();
         if ($body instanceof ReadableStreamInterface && $body->isReadable()) {
             $that = $this;
-            $body->on('close', function () use ($that, $deferred, &$timeout) {
+            $body->on('close', function () use ($that, $deferred, $state, &$timeout) {
                 if ($timeout >= 0) {
-                    $that->applyTimeout($deferred, $timeout);
+                    $that->applyTimeout($deferred, $state, $timeout);
                 }
             });
         } else {
-            $this->applyTimeout($deferred, $timeout);
+            $this->applyTimeout($deferred, $state, $timeout);
         }
 
         return $deferred->promise();
@@ -120,53 +119,51 @@ function ($e) use ($deferred, $loop, &$timeout) {
 
     /**
      * @internal
-     * @param Deferred $deferred
-     * @param number  $timeout
+     * @param number $timeout
      * @return void
      */
-    public function applyTimeout(Deferred $deferred, $timeout)
+    public function applyTimeout(Deferred $deferred, ClientRequestState $state, $timeout)
     {
-        $deferred->timeout = $this->loop->addTimer($timeout, function () use ($timeout, $deferred) {
+        $state->timeout = $this->loop->addTimer($timeout, function () use ($timeout, $deferred, $state) {
             $deferred->reject(new \RuntimeException(
                 'Request timed out after ' . $timeout . ' seconds'
             ));
-            if (isset($deferred->pending)) {
-                $deferred->pending->cancel();
-                unset($deferred->pending);
+            if ($state->pending !== null) {
+                $state->pending->cancel();
+                $state->pending = null;
             }
         });
     }
 
-    private function next(RequestInterface $request, Deferred $deferred)
+    private function next(RequestInterface $request, Deferred $deferred, ClientRequestState $state)
     {
         $this->progress('request', array($request));
 
         $that = $this;
-        ++$deferred->numRequests;
+        ++$state->numRequests;
 
         $promise = $this->sender->send($request);
 
         if (!$this->streaming) {
-            $promise = $promise->then(function ($response) use ($deferred, $that) {
-                return $that->bufferResponse($response, $deferred);
+            $promise = $promise->then(function ($response) use ($deferred, $state, $that) {
+                return $that->bufferResponse($response, $deferred, $state);
             });
         }
 
-        $deferred->pending = $promise;
+        $state->pending = $promise;
 
         return $promise->then(
-            function (ResponseInterface $response) use ($request, $that, $deferred) {
-                return $that->onResponse($response, $request, $deferred);
+            function (ResponseInterface $response) use ($request, $that, $deferred, $state) {
+                return $that->onResponse($response, $request, $deferred, $state);
             }
         );
     }
 
     /**
      * @internal
-     * @param ResponseInterface $response
      * @return PromiseInterface Promise<ResponseInterface, Exception>
      */
-    public function bufferResponse(ResponseInterface $response, $deferred)
+    public function bufferResponse(ResponseInterface $response, Deferred $deferred, ClientRequestState $state)
     {
         $stream = $response->getBody();
 
@@ -205,26 +202,24 @@ function ($e) use ($stream, $maximumSize) {
             }
         );
 
-        $deferred->pending = $promise;
+        $state->pending = $promise;
 
         return $promise;
     }
 
     /**
      * @internal
-     * @param ResponseInterface $response
-     * @param RequestInterface $request
      * @throws ResponseException
      * @return ResponseInterface|PromiseInterface
      */
-    public function onResponse(ResponseInterface $response, RequestInterface $request, $deferred)
+    public function onResponse(ResponseInterface $response, RequestInterface $request, Deferred $deferred, ClientRequestState $state)
     {
         $this->progress('response', array($response, $request));
 
         // follow 3xx (Redirection) response status codes if Location header is present and not explicitly disabled
         // @link https://tools.ietf.org/html/rfc7231#section-6.4
         if ($this->followRedirects && ($response->getStatusCode() >= 300 && $response->getStatusCode() < 400) && $response->hasHeader('Location')) {
-            return $this->onResponseRedirect($response, $request, $deferred);
+            return $this->onResponseRedirect($response, $request, $deferred, $state);
         }
 
         // only status codes 200-399 are considered to be valid, reject otherwise
@@ -242,7 +237,7 @@ public function onResponse(ResponseInterface $response, RequestInterface $reques
      * @return PromiseInterface
      * @throws \RuntimeException
      */
-    private function onResponseRedirect(ResponseInterface $response, RequestInterface $request, Deferred $deferred)
+    private function onResponseRedirect(ResponseInterface $response, RequestInterface $request, Deferred $deferred, ClientRequestState $state)
     {
         // resolve location relative to last request URI
         $location = Uri::resolve($request->getUri(), $response->getHeaderLine('Location'));
@@ -250,11 +245,11 @@ private function onResponseRedirect(ResponseInterface $response, RequestInterfac
         $request = $this->makeRedirectRequest($request, $location);
         $this->progress('redirect', array($request));
 
-        if ($deferred->numRequests >= $this->maxRedirects) {
+        if ($state->numRequests >= $this->maxRedirects) {
             throw new \RuntimeException('Maximum number of redirects (' . $this->maxRedirects . ') exceeded');
         }
 
-        return $this->next($request, $deferred);
+        return $this->next($request, $deferred, $state);
     }
 
     /**
diff --git a/tests/HttpServerTest.php b/tests/HttpServerTest.php
index 4d00fcef..31bc32ee 100644
--- a/tests/HttpServerTest.php
+++ b/tests/HttpServerTest.php
@@ -17,6 +17,9 @@ final class HttpServerTest extends TestCase
     private $connection;
     private $socket;
 
+    /** @var ?int */
+    private $called = null;
+
     /**
      * @before
      */
diff --git a/tests/Io/StreamingServerTest.php b/tests/Io/StreamingServerTest.php
index 2703362a..a2700b86 100644
--- a/tests/Io/StreamingServerTest.php
+++ b/tests/Io/StreamingServerTest.php
@@ -17,6 +17,9 @@ class StreamingServerTest extends TestCase
     private $connection;
     private $socket;
 
+    /** @var ?int */
+    private $called = null;
+
     /**
      * @before
      */