diff --git a/lib/Buzz/Client/Curl.php b/lib/Buzz/Client/Curl.php
index b7369de7..c1639837 100644
--- a/lib/Buzz/Client/Curl.php
+++ b/lib/Buzz/Client/Curl.php
@@ -47,7 +47,7 @@ static protected function setCurlOptsFromRequest($curl, Message\Request $request
                 if (is_array($fields)) {
                     $options[CURLOPT_HTTPHEADER] = array_filter($options[CURLOPT_HTTPHEADER], function($header)
                     {
-                        return 0 !== strpos($header, 'Content-Type: ');
+                        return 0 !== stripos($header, 'Content-Type: ');
                     });
                 }
                 break;
diff --git a/lib/Buzz/Message/Request.php b/lib/Buzz/Message/Request.php
index 7722b3b3..b1740294 100644
--- a/lib/Buzz/Message/Request.php
+++ b/lib/Buzz/Message/Request.php
@@ -162,7 +162,7 @@ private function mergeCookieHeaders(array $headers)
         $needle = 'Cookie:';
 
         foreach ($headers as $i => $header) {
-            if (0 !== strpos($header, $needle)) {
+            if (0 !== stripos($header, $needle)) {
                 continue;
             }