diff --git a/README.md b/README.md
index 1a01df7..425484b 100644
--- a/README.md
+++ b/README.md
@@ -14,7 +14,16 @@ Event-driven, streaming HTTP client for [ReactPHP](http://reactphp.org)
 
 ## Basic usage
 
-Requests are prepared using the ``Client#request()`` method.
+The `request(string $method, string $uri, array $headers = array(), string $version = '1.0'): Request`
+method can be used to prepare new Request objects.
+
+The optional `$headers` parameter can be used to pass additional request
+headers.
+You can use an associative array (key=value) or an array for each header value
+(key=values).
+The Request will automatically include an appropriate `Host`,
+`User-Agent: react/alpha` and `Connection: close` header if applicable.
+You can pass custom header values or use an empty array to omit any of these.
 
 The `Request#write(string $data)` method can be used to
 write data to the request body.
diff --git a/src/RequestData.php b/src/RequestData.php
index 961db22..e9e39e5 100644
--- a/src/RequestData.php
+++ b/src/RequestData.php
@@ -73,8 +73,10 @@ public function __toString()
 
         $data = '';
         $data .= "{$this->method} {$this->getPath()} HTTP/{$this->protocolVersion}\r\n";
-        foreach ($headers as $name => $value) {
-            $data .= "$name: $value\r\n";
+        foreach ($headers as $name => $values) {
+            foreach ((array)$values as $value) {
+                $data .= "$name: $value\r\n";
+            }
         }
         $data .= "\r\n";
 
diff --git a/tests/RequestDataTest.php b/tests/RequestDataTest.php
index 6fc8f15..9d63f8d 100644
--- a/tests/RequestDataTest.php
+++ b/tests/RequestDataTest.php
@@ -34,6 +34,26 @@ public function toStringReturnsHTTPRequestMessageWithProtocolVersion()
         $this->assertSame($expected, $requestData->__toString());
     }
 
+    /** @test */
+    public function toStringReturnsHTTPRequestMessageWithHeaders()
+    {
+        $requestData = new RequestData('GET', 'http://www.example.com', array(
+            'User-Agent' => array(),
+            'Via' => array(
+                'first',
+                'second'
+            )
+        ));
+
+        $expected = "GET / HTTP/1.0\r\n" .
+            "Host: www.example.com\r\n" .
+            "Via: first\r\n" .
+            "Via: second\r\n" .
+            "\r\n";
+
+        $this->assertSame($expected, $requestData->__toString());
+    }
+
     /** @test */
     public function toStringReturnsHTTPRequestMessageWithProtocolVersionThroughConstructor()
     {