diff --git a/src/Traits/Request.php b/src/Traits/Request.php
index aa8d172..5d821f3 100644
--- a/src/Traits/Request.php
+++ b/src/Traits/Request.php
@@ -148,7 +148,7 @@ public function setBasicAuth(string $userName, string $password)
     public function setHeader(string $key, string $value, $strtolower = true)
     {
         if ($strtolower) {
-            $this->header[strtolower($key)] = strtolower($value);
+            $this->header[strtolower($key)] = $value;
         } else {
             $this->header[$key] = $value;
         }