diff --git a/src/applications/transactions/engineextension/PhabricatorSubtypeEditEngineExtension.php b/src/applications/transactions/engineextension/PhabricatorSubtypeEditEngineExtension.php
--- a/src/applications/transactions/engineextension/PhabricatorSubtypeEditEngineExtension.php
+++ b/src/applications/transactions/engineextension/PhabricatorSubtypeEditEngineExtension.php
@@ -21,7 +21,7 @@
   public function supportsObject(
     PhabricatorEditEngine $engine,
     PhabricatorApplicationTransactionInterface $object) {
-    return $engine->supportsSubtypes();
+    return ($object instanceof PhabricatorEditEngineSubtypeInterface);
   }
 
   public function buildCustomEditFields(