Carry over request uri scheme.

src/Client.php

@@ -33,7 +33,9 @@ class Client implements ClientInterface
     {
         $serializedRequest = Serializer::toString($request);
         $zendRequest = ZendRequest::fromString($serializedRequest);
-        $zendRequest->getUri()->setHost($request->getUri()->getHost());
+        $requestHost = ($requestUri = $request->getUri())->getHost();
+        ($zendRequestUri = $zendRequest->getUri())->setHost($requestHost);
+        $zendRequestUri->setScheme($requestUri->getScheme());
 
         try {
             $zendResponse = $this->zendClient->send($zendRequest);