diff --git a/sys/thing/properties.h b/sys/thing/properties.h
index 6e26337..2ccf20e 100644
--- a/sys/thing/properties.h
+++ b/sys/thing/properties.h
@@ -47,7 +47,7 @@
 public mixed Query(string name, int Type = F_VALUE);
 
 // filtered property access
-public mixed SetProp(string name, mixed Value);
+public mixed SetProp(string name, mixed Value, int drop_priv = extern_call());
 public mixed QueryProp(string name);
 
 // global property handling