diff --git a/src/AWS/CRT/HTTP/Headers.php b/src/AWS/CRT/HTTP/Headers.php
index 9a04bd3..4744182 100644
--- a/src/AWS/CRT/HTTP/Headers.php
+++ b/src/AWS/CRT/HTTP/Headers.php
@@ -42,6 +42,6 @@ final class Headers {
     }
 
     public function toArray() {
-        return array_merge($this->headers);
+        return $this->headers;
     }
 }
diff --git a/src/AWS/CRT/HTTP/Message.php b/src/AWS/CRT/HTTP/Message.php
index e186daf..a148f16 100644
--- a/src/AWS/CRT/HTTP/Message.php
+++ b/src/AWS/CRT/HTTP/Message.php
@@ -3,7 +3,6 @@
 namespace AWS\CRT\HTTP;
 
 use AWS\CRT\NativeResource;
-
 use AWS\CRT\Internal\Encoding;
 
 abstract class Message extends NativeResource {
@@ -12,11 +11,11 @@ abstract class Message extends NativeResource {
     private $query;
     private $headers;
 
-    public function __construct($method, $path, $query = [], $headers = null) {
+    public function __construct($method, $path, $query = [], $headers = []) {
         $this->method = $method;
         $this->path = $path;
         $this->query = $query;
-        $this->headers = !is_null($headers) ? $headers : new Headers();
+        $this->headers = new Headers($headers);
         $this->acquire(self::$crt->http_message_new_from_blob(self::marshall($this)));
     }
 
@@ -54,7 +53,7 @@ abstract class Message extends NativeResource {
             $query = [];
         }
 
-        return new $class($method, $path, $query, $headers);
+        return new $class($method, $path, $query, $headers->toArray());
     }
 
     public function pathAndQuery() {
diff --git a/src/AWS/CRT/HTTP/Request.php b/src/AWS/CRT/HTTP/Request.php
index 18d908e..302b7c0 100644
--- a/src/AWS/CRT/HTTP/Request.php
+++ b/src/AWS/CRT/HTTP/Request.php
@@ -2,11 +2,16 @@
 
 namespace AWS\CRT\HTTP;
 
+use AWS\CRT\IO\InputStream;
+
 class Request extends Message {
     private $body_stream = null;
 
-    public function __construct($method, $path, $query = [], $headers = null, $body_stream = null) {
+    public function __construct($method, $path, $query = [], $headers = [], $body_stream = null) {
         parent::__construct($method, $path, $query, $headers);
+        if (!is_null($body_stream) && !($body_stream instanceof InputStream)) {
+            throw \InvalidArgumentException('body_stream must be an ' . InputStream::class);
+        }
         $this->body_stream = $body_stream;
     }
 
diff --git a/src/tests/HttpMessageTest.php b/src/tests/HttpMessageTest.php
index bf0f87b..4928e90 100644
--- a/src/tests/HttpMessageTest.php
+++ b/src/tests/HttpMessageTest.php
@@ -37,11 +37,10 @@ final class HttpMessageTest extends CrtTestCase {
     }
 
     public function testRequestMarshalling() {
-        $headers_array = [
+        $headers = [
             "host" => "s3.amazonaws.com",
             "test" => "this is a test header value"
         ];
-        $headers = new Headers($headers_array);
         $method = "GET";
         $path = "/index.php";
         $query = [];
@@ -54,11 +53,10 @@ final class HttpMessageTest extends CrtTestCase {
     }
 
     public function testRequestMarshallingWithQueryParams() {
-        $headers_array = [
+        $headers = [
             "host" => "s3.amazonaws.com",
             "test" => "this is a test header value"
         ];
-        $headers = new Headers($headers_array);
         $method = "GET";
         $path = "/index.php";
         $query = [
@@ -76,18 +74,17 @@ final class HttpMessageTest extends CrtTestCase {
     }
 
     public function testResponseMarshalling() {
-        $headers_array = [
+        $headers = [
             "content-length" => "42",
             "test" => "this is a test header value"
         ];
-        $headers = new Headers($headers_array);
         $method = "GET";
         $path = "/index.php";
         $query = [
             'response' => '1'
         ];
 
-        $msg = new Response($method, $path, $query, $headers, 400);
+        $msg = new Response($method, $path, $query, $headers, 200);
         $msg_buf = Request::marshall($msg);
         $msg_copy = Request::unmarshall($msg_buf);