diff --git a/system/HTTP/CURLRequest.php b/system/HTTP/CURLRequest.php
index 4c011c985f1d..35b62ec3486f 100644
--- a/system/HTTP/CURLRequest.php
+++ b/system/HTTP/CURLRequest.php
@@ -482,7 +482,11 @@ protected function setResponseHeaders(array $headers = [])
                 $title = trim(substr($header, 0, $pos));
                 $value = trim(substr($header, $pos + 1));
 
-                $this->response->addHeader($title, $value);
+                if ($this->response instanceof Response) {
+                    $this->response->addHeader($title, $value);
+                } else {
+                    $this->response->setHeader($title, $value);
+                }
             } elseif (strpos($header, 'HTTP') === 0) {
                 preg_match('#^HTTP\/([12](?:\.[01])?) (\d+) (.+)#', $header, $matches);