diff --git a/core/tests/Drupal/FunctionalJavascriptTests/WebDriverCurlService.php b/core/tests/Drupal/FunctionalJavascriptTests/WebDriverCurlService.php
index 13991afd5d..eba9dcce7a 100644
--- a/core/tests/Drupal/FunctionalJavascriptTests/WebDriverCurlService.php
+++ b/core/tests/Drupal/FunctionalJavascriptTests/WebDriverCurlService.php
@@ -42,6 +42,7 @@ public function execute($requestMethod, $url, $parameters = NULL, $extraOptions
             }
             else {
               $customHeaders[] = 'Content-Length: 0';
+              $customHeaders[] = 'Transfer-Encoding:';
             }
 
             // Suppress "Expect: 100-continue" header automatically added by
@@ -62,6 +63,7 @@ public function execute($requestMethod, $url, $parameters = NULL, $extraOptions
             }
             else {
               $customHeaders[] = 'Content-Length: 0';
+              $customHeaders[] = 'Transfer-Encoding:';
             }
 
             // Suppress "Expect: 100-continue" header automatically added by