diff --git a/src/applications/differential/config/PhabricatorDifferentialConfigOptions.php b/src/applications/differential/config/PhabricatorDifferentialConfigOptions.php
--- a/src/applications/differential/config/PhabricatorDifferentialConfigOptions.php
+++ b/src/applications/differential/config/PhabricatorDifferentialConfigOptions.php
@@ -86,6 +86,7 @@
         array(
           '/\.py$/',
           '/\.l?hs$/',
+          '/\.ya?ml$/',
         ))
         ->setDescription(
           pht(