diff --git a/src/Browser.php b/src/Browser.php
index bb475c59..16c98fb3 100644
--- a/src/Browser.php
+++ b/src/Browser.php
@@ -847,6 +847,7 @@ private function requestMayBeStreaming($method, $url, array $headers = array(),
             foreach (\array_keys($headers) as $headerKey) {
                 if (\strcasecmp($headerKey, $key) === 0) {
                     $explicitHeaderExists = true;
+                    break;
                 }
             }
             if (!$explicitHeaderExists) {