diff --git a/private/attributes b/private/attributes
index 3d18d71..cf1c307 100644
--- a/private/attributes
+++ b/private/attributes
@@ -4,3 +4,8 @@
 # to exempt them from recent mls changes. It must not be applied
 # to any domain on newer system or vendor image.
 attribute mlsvendorcompat;
+
+# Attributes for property types having both system_property_type
+# and vendor_property_type. Such types are ill-formed because
+# property owner attributes must be exclusive.
+attribute system_and_vendor_property_type;