diff --git a/moo/kernel/Socket.moo b/moo/kernel/Socket.moo
index f04dc8c..b060261 100644
--- a/moo/kernel/Socket.moo
+++ b/moo/kernel/Socket.moo
@@ -204,7 +204,7 @@ class(#byte(16)) IP6Address(IP4Address)
 	}
 }
 
-class(#byte) IP4SocketAddress(IP4Address)
+class(#byte(19)) IP6SocketAddress(IP6Address)
 {
 	method(#class) new
 	{
diff --git a/moo/lib/comp.c b/moo/lib/comp.c
index 52a514a..c0b895b 100644
--- a/moo/lib/comp.c
+++ b/moo/lib/comp.c
@@ -6931,6 +6931,8 @@ static int make_defined_class (moo_t* moo)
 
 	if (moo->c->cls.type_size > 0)
 	{
+		/* class(#byte(N)), class(#word(N)), etc */
+/* TODO: ensure that this size is equal to greater than the type size of the parent */
 		MOO_ASSERT (moo, moo->c->cls.var[VAR_INSTANCE].total_count == 0);
 		MOO_ASSERT (moo, moo->c->cls.indexed_type != MOO_OBJ_TYPE_OOP);
 		spec = MOO_CLASS_SPEC_MAKE (moo->c->cls.type_size, flags, moo->c->cls.indexed_type);
@@ -7227,7 +7229,7 @@ static int __compile_class_definition (moo_t* moo, int extend)
 					/* invalid modifier */
 					set_syntax_error (moo, MOO_SYNERR_MODIFIERINVAL, TOKEN_LOC(moo), TOKEN_NAME(moo));
 					return -1;
-				}size 16 specified for fixed-sized(4) class IP6Addre
+				}
 
 				if (permit_type_size)
 				{
@@ -7370,8 +7372,7 @@ static int __compile_class_definition (moo_t* moo, int extend)
 		{
 			super_is_nil = 1;
 		}
-		else if (TOKEN_TYPE(moo) != MOO_IOTOK_IDENT &&
-			    TOKEN_TYPE(moo) != MOO_IOTOK_IDENT_DOTTED)
+		else if (TOKEN_TYPE(moo) != MOO_IOTOK_IDENT && TOKEN_TYPE(moo) != MOO_IOTOK_IDENT_DOTTED)
 		{
 			/* superclass name expected */
 			set_syntax_error (moo, MOO_SYNERR_IDENT, TOKEN_LOC(moo), TOKEN_NAME(moo));
@@ -7501,6 +7502,7 @@ static int __compile_class_definition (moo_t* moo, int extend)
 		return -1;
 	}
 
+	MOO_ASSERT (moo, moo->c->cls.super_oop != MOO_NULL);
 	if (moo->c->cls.super_oop != moo->_nil)
 	{
 		/* adjust the instance variable count and the class instance variable
@@ -7515,7 +7517,21 @@ static int __compile_class_definition (moo_t* moo, int extend)
 		/* [NOTE] class variables are not inherited. 
 		 *        so no data about them are not transferred over */
 
-		moo->c->cls.var[VAR_INSTANCE].total_count = MOO_CLASS_SPEC_NAMED_INSTVARS(spec);
+		
+		if ((moo->c->cls.flags & CLASS_INDEXED) && moo->c->cls.indexed_type != MOO_OBJ_TYPE_OOP)
+		{
+			/* TODO: do i need to check if the parent class and the current class have the same indexed type? */
+			if (moo->c->cls.type_size < MOO_CLASS_SPEC_NAMED_INSTVARS(spec))
+			{
+				set_syntax_error (moo, MOO_SYNERR_CLASSTSIZEINVAL, TOKEN_LOC(moo), TOKEN_NAME(moo)); /* TODO: change error location... */
+				return -1;
+			}
+		}
+		else
+		{
+			MOO_ASSERT (moo, moo->c->cls.type_size == 0); /* no such thing as class(#pointer(N)). so it must be 0 */
+			moo->c->cls.var[VAR_INSTANCE].total_count = MOO_CLASS_SPEC_NAMED_INSTVARS(spec);
+		}
 		moo->c->cls.var[VAR_CLASSINST].total_count = MOO_CLASS_SELFSPEC_CLASSINSTVARS(self_spec);
 	}
 
diff --git a/moo/lib/obj.c b/moo/lib/obj.c
index ae164b8..8627271 100644
--- a/moo/lib/obj.c
+++ b/moo/lib/obj.c
@@ -191,6 +191,7 @@ static MOO_INLINE int decode_spec (moo_t* moo, moo_oop_class_t _class, moo_oow_t
 	{
 		indexed_type = MOO_CLASS_SPEC_INDEXED_TYPE(spec);
 
+#if 0
 		if (indexed_type == MOO_OBJ_TYPE_OOP)
 		{
 			if (named_instvar > MOO_MAX_NAMED_INSTVARS)
@@ -209,27 +210,38 @@ static MOO_INLINE int decode_spec (moo_t* moo, moo_oop_class_t _class, moo_oow_t
 		else
 		{
 			/* a non-pointer indexed class can't have named instance variables */
-#if 0
-			if (named_instvar > 0) 
+			if (named_instvar > MOO_) 
 			{
 				moo_seterrbfmt (moo, MOO_EINVAL, "named instance variables in a variable-nonpointer class %O", _class);
 				return -1;
 			}
-#else
-			if (named_instvar > 0 && vlen > 0) 
-			{
-				/* disallow the user-defined length if the fixed type size is specified 
-				 * and it's greater than 0, the user-defined length is not allowed */
-				moo_seterrbfmt (moo, MOO_EINVAL, "size %zu specified for fixed-sized(%zu) class %O", vlen, named_instvar, _class); 
-				return -1;
-			}
-#endif
 			if (vlen > MOO_OBJ_SIZE_MAX) 
 			{
 				moo_seterrbfmt (moo, MOO_EINVAL, "too many unnamed instance variables for a variable-nonpointer class %O - %zu/%zu", _class, vlen, (moo_oow_t)MOO_OBJ_SIZE_MAX); 
 				return -1;
 			}
 		}
+#else
+		/* the size of the fixed area for non-pointer objects are supported.
+		 * the fixed area of a pointer object holds named instance variables 
+		 * and a non-pointer object is facilitated with the fixed area of the size
+		 * specified in the class description like #byte(5), #word(10).
+		 * 
+		 * when it comes to spec decoding, there is no different between a pointer
+		 * object and a non-pointer object */
+		if (named_instvar > MOO_MAX_NAMED_INSTVARS)
+		{
+			moo_seterrbfmt (moo, MOO_EINVAL, "too many fixed fields for a class %O - %zu/%zu", _class, named_instvar, (moo_oow_t)MOO_MAX_NAMED_INSTVARS); 
+			return -1;
+		}
+		if (vlen > MOO_MAX_INDEXED_INSTVARS(named_instvar))
+		{
+			moo_seterrbfmt (moo, MOO_EINVAL, "too many variable fields for a class %O - %zu/%zu", _class, vlen, (moo_oow_t)MOO_MAX_INDEXED_INSTVARS(named_instvar)); 
+			return -1;
+		}
+
+		MOO_ASSERT (moo, named_instvar + vlen <= MOO_OBJ_SIZE_MAX);
+#endif
 	}
 	else
 	{