diff --git a/src/applications/config/check/PhabricatorSetupCheckExtensions.php b/src/applications/config/check/PhabricatorSetupCheckExtensions.php
--- a/src/applications/config/check/PhabricatorSetupCheckExtensions.php
+++ b/src/applications/config/check/PhabricatorSetupCheckExtensions.php
@@ -16,6 +16,7 @@
       'openssl',
       'mbstring',
       'iconv',
+      'ctype',
 
       // There is a chance we might not need this, but some configurations (like
       // OAuth or Amazon SES) will require it. Just mark it 'required' since