diff --git a/lib/Buzz/Message/AbstractMessage.php b/lib/Buzz/Message/AbstractMessage.php
index 5f9d5340..fa51be9c 100644
--- a/lib/Buzz/Message/AbstractMessage.php
+++ b/lib/Buzz/Message/AbstractMessage.php
@@ -95,7 +95,7 @@ public function toDomDocument()
 
     public function setHeaders(array $headers)
     {
-        $this->headers = $headers;
+        $this->headers = $this->flattenHeaders($headers);
     }
 
     public function addHeader($header)
@@ -105,7 +105,7 @@ public function addHeader($header)
 
     public function addHeaders(array $headers)
     {
-        $this->headers = array_merge($this->headers, $headers);
+        $this->headers = array_merge($this->headers, $this->flattenHeaders($headers));
     }
 
     public function getHeaders()
@@ -133,4 +133,18 @@ public function __toString()
 
         return $string;
     }
+
+    protected function flattenHeaders(array $headers)
+    {
+        $flattened = array();
+        foreach ($headers as $key => $header) {
+            if (is_int($key)) {
+                $flattened[] = $header;
+            } else {
+                $flattened[] = $key.': '.$header;
+            }
+        }
+
+        return $flattened;
+    }
 }
diff --git a/lib/Buzz/Message/Request.php b/lib/Buzz/Message/Request.php
index 6ef3a3dc..07f6591e 100644
--- a/lib/Buzz/Message/Request.php
+++ b/lib/Buzz/Message/Request.php
@@ -29,12 +29,8 @@ public function setHeaders(array $headers)
     {
         parent::setHeaders(array());
 
-        foreach ($headers as $key => $header) {
-            if (is_int($key)) {
-                $this->addHeader($header);
-            } else {
-                $this->addHeader($key.': '.$header);
-            }
+        foreach ($this->flattenHeaders($headers) as $header) {
+            $this->addHeader($header);
         }
     }