diff --git a/src/macros.py b/src/macros.py
index b4be15b..643a285 100644
--- a/src/macros.py
+++ b/src/macros.py
@@ -115,7 +115,8 @@
 # Macro for ECMAScript 5 queries of the type:
 # "Type(O) is object."
 # This is the same as being either a function or an object in V8 terminology.
-macro IS_SPEC_OBJECT_OR_NULL(arg) = (%_IsObject(arg) || %_IsFunction(arg));
+# In addition, an undetectable object is also included by this.
+macro IS_SPEC_OBJECT(arg) = (%_IsSpecObject(arg));
 
 # Inline macros. Use %IS_VAR to make sure arg is evaluated only once.
 macro NUMBER_IS_NAN(arg) = (!%_IsSmi(%IS_VAR(arg)) && !(arg == arg));