diff --git a/src/applications/config/check/PhabricatorWebServerSetupCheck.php b/src/applications/config/check/PhabricatorWebServerSetupCheck.php
--- a/src/applications/config/check/PhabricatorWebServerSetupCheck.php
+++ b/src/applications/config/check/PhabricatorWebServerSetupCheck.php
@@ -58,6 +58,7 @@
       $gzip_future = id(new HTTPSFuture($base_uri))
         ->addHeader('X-Setup-SelfCheck', 1)
         ->addHeader('Content-Encoding', 'gzip')
+        ->setMethod('POST')
         ->setTimeout(5)
         ->setData($gzip_compressed);