diff --git a/lib/class.js b/lib/class.js
index 209b46a..41c1a73 100644
--- a/lib/class.js
+++ b/lib/class.js
@@ -300,7 +300,6 @@ function setupProps( func, abstract_methods )
 {
     attachAbstract( func, abstract_methods );
     attachExtend( func );
-    attachInstanceOf( func );
 }