diff --git a/moo/configure b/moo/configure
index 8abe074..0ad318f 100755
--- a/moo/configure
+++ b/moo/configure
@@ -1504,7 +1504,8 @@ Optional Features:
   --enable-ltdl-install   install libltdl
   --enable-debug          build the library in the debug mode (default. no)
   --enable-unicode        Use the unicode character type as the default
-                          character type (default. yes)
+                          character type. one of yes, no, ucs2, ucs4 (default.
+                          yes)
   --enable-cxx            build the library for C++ if a C++ compiler is
                           available (default. yes)
   --enable-dynamic-module enable dynamic module capability(default. yes)
@@ -22521,7 +22522,6 @@ $as_echo "#define MOO_BUILD_RELEASE 1" >>confdefs.h
 
 fi
 
-
 # Check whether --enable-unicode was given.
 if test "${enable_unicode+set}" = set; then :
   enableval=$enable_unicode; enable_unicode=$enableval
@@ -22535,6 +22535,16 @@ then
 
 $as_echo "#define MOO_ENABLE_UNICODE 1" >>confdefs.h
 
+elif test "${enable_unicode}" = "ucs2"
+then
+
+$as_echo "#define MOO_ENABLE_UNICODE 2" >>confdefs.h
+
+elif test "${enable_unicode}" = "ucs4"
+then
+
+$as_echo "#define MOO_ENABLE_UNICODE 4" >>confdefs.h
+
 fi
 
 # Check whether --enable-cxx was given.
diff --git a/moo/configure.ac b/moo/configure.ac
index 1fd2036..e101640 100644
--- a/moo/configure.ac
+++ b/moo/configure.ac
@@ -645,15 +645,20 @@ else
 	AC_SUBST(BUILD_MODE, "release")
 fi
 
-
 AC_ARG_ENABLE([unicode],
-	[AS_HELP_STRING([--enable-unicode],[Use the unicode character type as the default character type (default. yes)])],
+	[AS_HELP_STRING([--enable-unicode],[Use the unicode character type as the default character type. one of yes, no, ucs2, ucs4 (default. yes)])],
 	enable_unicode=$enableval,
 	enable_unicode=yes
 )
 if test "${enable_unicode}" = "yes"
 then
 	AC_DEFINE([MOO_ENABLE_UNICODE],[1],[Use the unicode character type as the default character type])
+elif test "${enable_unicode}" = "ucs2"
+then
+	AC_DEFINE([MOO_ENABLE_UNICODE],[2],[Use the unicode character type as the default character type])
+elif test "${enable_unicode}" = "ucs4"
+then
+	AC_DEFINE([MOO_ENABLE_UNICODE],[4],[Use the unicode character type as the default character type])
 fi
 
 AC_ARG_ENABLE([cxx], 
diff --git a/moo/lib/bigint.c b/moo/lib/bigint.c
index 3e6c2f1..e458b0a 100644
--- a/moo/lib/bigint.c
+++ b/moo/lib/bigint.c
@@ -1,7 +1,7 @@
 /*
  * $Id$
  *
-    Copyright (c) 2014-2017 Chung, Hyung-Hwan. All rights reserved.
+    Copyright (c) 2014-2018 Chung, Hyung-Hwan. All rights reserved.
 
     Redistribution and use in source and binary forms, with or without
     modification, are permitted provided that the following conditions
diff --git a/moo/lib/comp.c b/moo/lib/comp.c
index 11bcc4d..e6bc29b 100644
--- a/moo/lib/comp.c
+++ b/moo/lib/comp.c
@@ -1,7 +1,7 @@
 /*
  * $Id$
  *
-    Copyright (c) 2014-2017 Chung, Hyung-Hwan. All rights reserved.
+    Copyright (c) 2014-2018 Chung, Hyung-Hwan. All rights reserved.
 
     Redistribution and use in source and binary forms, with or without
     modification, are permitted provided that the following conditions
diff --git a/moo/lib/debug.c b/moo/lib/debug.c
index 697d33f..de89233 100644
--- a/moo/lib/debug.c
+++ b/moo/lib/debug.c
@@ -1,7 +1,7 @@
 /*
  * $Id$
  *
-    Copyright (c) 2014-2017 Chung, Hyung-Hwan. All rights reserved.
+    Copyright (c) 2014-2018 Chung, Hyung-Hwan. All rights reserved.
 
     Redistribution and use in source and binary forms, with or without
     modification, are permitted provided that the following conditions
diff --git a/moo/lib/decode.c b/moo/lib/decode.c
index a011179..11fd0f1 100644
--- a/moo/lib/decode.c
+++ b/moo/lib/decode.c
@@ -1,7 +1,7 @@
 /*
  * $Id$
  *
-    Copyright (c) 2014-2017 Chung, Hyung-Hwan. All rights reserved.
+    Copyright (c) 2014-2018 Chung, Hyung-Hwan. All rights reserved.
 
     Redistribution and use in source and binary forms, with or without
     modification, are permitted provided that the following conditions
diff --git a/moo/lib/dic.c b/moo/lib/dic.c
index e325a54..56367fe 100644
--- a/moo/lib/dic.c
+++ b/moo/lib/dic.c
@@ -1,7 +1,7 @@
 /*
  * $Id$
  *
-    Copyright (c) 2014-2017 Chung, Hyung-Hwan. All rights reserved.
+    Copyright (c) 2014-2018 Chung, Hyung-Hwan. All rights reserved.
 
     Redistribution and use in source and binary forms, with or without
     modification, are permitted provided that the following conditions
diff --git a/moo/lib/err.c b/moo/lib/err.c
index 1348bd6..fc38cc3 100644
--- a/moo/lib/err.c
+++ b/moo/lib/err.c
@@ -1,7 +1,7 @@
 /*
  * $Id$
  *
-    Copyright (c) 2014-2017 Chung, Hyung-Hwan. All rights reserved.
+    Copyright (c) 2014-2018 Chung, Hyung-Hwan. All rights reserved.
 
     Redistribution and use in source and binary forms, with or without
     modification, are permitted provided that the following conditions
diff --git a/moo/lib/exec.c b/moo/lib/exec.c
index bf83077..cce37e9 100644
--- a/moo/lib/exec.c
+++ b/moo/lib/exec.c
@@ -1,7 +1,7 @@
 /*
  * $Id$
  *
-    Copyright (c) 2014-2017 Chung, Hyung-Hwan. All rights reserved.
+    Copyright (c) 2014-2018 Chung, Hyung-Hwan. All rights reserved.
 
     Redistribution and use in source and binary forms, with or without
     modification, are permitted provided that the following conditions
diff --git a/moo/lib/gc.c b/moo/lib/gc.c
index dbff985..b6e1216 100644
--- a/moo/lib/gc.c
+++ b/moo/lib/gc.c
@@ -1,7 +1,7 @@
 /*
  * $Id$
  *
-    Copyright (c) 2014-2017 Chung, Hyung-Hwan. All rights reserved.
+    Copyright (c) 2014-2018 Chung, Hyung-Hwan. All rights reserved.
 
     Redistribution and use in source and binary forms, with or without
     modification, are permitted provided that the following conditions
diff --git a/moo/lib/heap.c b/moo/lib/heap.c
index aebecfb..30ab517 100644
--- a/moo/lib/heap.c
+++ b/moo/lib/heap.c
@@ -1,7 +1,7 @@
 /*
  * $Id$
  *
-    Copyright (c) 2014-2017 Chung, Hyung-Hwan. All rights reserved.
+    Copyright (c) 2014-2018 Chung, Hyung-Hwan. All rights reserved.
 
     Redistribution and use in source and binary forms, with or without
     modification, are permitted provided that the following conditions
diff --git a/moo/lib/logfmt.c b/moo/lib/logfmt.c
index 03f3681..51aa087 100644
--- a/moo/lib/logfmt.c
+++ b/moo/lib/logfmt.c
@@ -1,7 +1,7 @@
 /*
  * $Id$
  *
-    Copyright (c) 2014-2017 Chung, Hyung-Hwan. All rights reserved.
+    Copyright (c) 2014-2018 Chung, Hyung-Hwan. All rights reserved.
 
     Redistribution and use in source and binary forms, with or without
     modification, are permitted provided that the following conditions
diff --git a/moo/lib/logfmtv.h b/moo/lib/logfmtv.h
index 37fa633..13e223b 100644
--- a/moo/lib/logfmtv.h
+++ b/moo/lib/logfmtv.h
@@ -1,7 +1,7 @@
 /*
  * $Id$
  *
-    Copyright (c) 2014-2017 Chung, Hyung-Hwan. All rights reserved.
+    Copyright (c) 2014-2018 Chung, Hyung-Hwan. All rights reserved.
 
     Redistribution and use in source and binary forms, with or without
     modification, are permitted provided that the following conditions
diff --git a/moo/lib/main.c b/moo/lib/main.c
index c7cd7ff..e35c88a 100644
--- a/moo/lib/main.c
+++ b/moo/lib/main.c
@@ -1,7 +1,7 @@
 /*
  * $Id$
  *
-    Copyright (c) 2014-2017 Chung, Hyung-Hwan. All rights reserved.
+    Copyright (c) 2014-2018 Chung, Hyung-Hwan. All rights reserved.
 
     Redistribution and use in source and binary forms, with or without
     modification, are permitted provided that the following conditions
diff --git a/moo/lib/moo-cmn.h b/moo/lib/moo-cmn.h
index 06c11df..092e5c8 100644
--- a/moo/lib/moo-cmn.h
+++ b/moo/lib/moo-cmn.h
@@ -1,7 +1,7 @@
 /*
  * $Id$
  *
-    Copyright (c) 2014-2017 Chung, Hyung-Hwan. All rights reserved.
+    Copyright (c) 2014-2018 Chung, Hyung-Hwan. All rights reserved.
 
     Redistribution and use in source and binary forms, with or without
     modification, are permitted provided that the following conditions
@@ -280,15 +280,26 @@ typedef unsigned char           moo_bchu_t; /* unsigned version of moo_bch_t for
 #define MOO_SIZEOF_BCH_T MOO_SIZEOF_CHAR
 #define MOO_SIZEOF_BCI_T MOO_SIZEOF_INT
 
-#if defined(__GNUC__) && defined(__CHAR16_TYPE__)
-/* TODO ... wchar_t???, char16_t? char32_t? */
-typedef __CHAR16_TYPE__         moo_uch_t; 
+#if defined(MOO_ENABLE_UNICODE) && (MOO_ENABLE_UNICODE == 4)
+#	if defined(__GNUC__) && defined(__CHAR32_TYPE__)
+	typedef __CHAR32_TYPE__    moo_uch_t;
+#	else
+	typedef moo_uint32_t       moo_uch_t;
+#	endif
+	typedef moo_uint32_t       moo_uchu_t; /* same as moo_uch_t as it is already unsigned */
+#	define MOO_SIZEOF_UCH_T 4
+
+#elif defined(__GNUC__) && defined(__CHAR16_TYPE__)
+	typedef __CHAR16_TYPE__    moo_uch_t; 
+	typedef moo_uint16_t       moo_uchu_t; /* same as moo_uch_t as it is already unsigned */
+#	define MOO_SIZEOF_UCH_T 2
 #else
-typedef moo_uint16_t            moo_uch_t;
+	typedef moo_uint16_t       moo_uch_t;
+	typedef moo_uint16_t       moo_uchu_t; /* same as moo_uch_t as it is already unsigned */
+#	define MOO_SIZEOF_UCH_T 2
 #endif
+
 typedef moo_int32_t             moo_uci_t;
-typedef moo_uint16_t            moo_uchu_t; /* same as moo_uch_t as it is already unsigned */
-#define MOO_SIZEOF_UCH_T 2
 #define MOO_SIZEOF_UCI_T 4
 
 typedef moo_uint8_t             moo_oob_t;
diff --git a/moo/lib/moo-opt.h b/moo/lib/moo-opt.h
index 1680894..e1c16de 100644
--- a/moo/lib/moo-opt.h
+++ b/moo/lib/moo-opt.h
@@ -1,7 +1,7 @@
 /*
  * $Id$
  *
-    Copyright (c) 2014-2017 Chung, Hyung-Hwan. All rights reserved.
+    Copyright (c) 2014-2018 Chung, Hyung-Hwan. All rights reserved.
 
     Redistribution and use in source and binary forms, with or without
     modification, are permitted provided that the following conditions
diff --git a/moo/lib/moo-prv.h b/moo/lib/moo-prv.h
index 9f09a11..f4f6b1f 100644
--- a/moo/lib/moo-prv.h
+++ b/moo/lib/moo-prv.h
@@ -1,7 +1,7 @@
 /*
  * $Id$
  *
-    Copyright (c) 2014-2017 Chung, Hyung-Hwan. All rights reserved.
+    Copyright (c) 2014-2018 Chung, Hyung-Hwan. All rights reserved.
 
     Redistribution and use in source and binary forms, with or without
     modification, are permitted provided that the following conditions
diff --git a/moo/lib/moo-rbt.h b/moo/lib/moo-rbt.h
index 142b633..6b37c80 100644
--- a/moo/lib/moo-rbt.h
+++ b/moo/lib/moo-rbt.h
@@ -1,7 +1,7 @@
 /*
  * $Id$
  *
-    Copyright (c) 2014-2017 Chung, Hyung-Hwan. All rights reserved.
+    Copyright (c) 2014-2018 Chung, Hyung-Hwan. All rights reserved.
 
     Redistribution and use in source and binary forms, with or without
     modification, are permitted provided that the following conditions
diff --git a/moo/lib/moo-utl.h b/moo/lib/moo-utl.h
index 7a2378b..9765b10 100644
--- a/moo/lib/moo-utl.h
+++ b/moo/lib/moo-utl.h
@@ -1,7 +1,7 @@
 /*
  * $Id$
  *
-    Copyright (c) 2014-2017 Chung, Hyung-Hwan. All rights reserved.
+    Copyright (c) 2014-2018 Chung, Hyung-Hwan. All rights reserved.
 
     Redistribution and use in source and binary forms, with or without
     modification, are permitted provided that the following conditions
diff --git a/moo/lib/moo.c b/moo/lib/moo.c
index fbe9b08..440647b 100644
--- a/moo/lib/moo.c
+++ b/moo/lib/moo.c
@@ -1,7 +1,7 @@
 /*
  * $Id$
  *
-    Copyright (c) 2014-2017 Chung, Hyung-Hwan. All rights reserved.
+    Copyright (c) 2014-2018 Chung, Hyung-Hwan. All rights reserved.
 
     Redistribution and use in source and binary forms, with or without
     modification, are permitted provided that the following conditions
diff --git a/moo/lib/moo.h b/moo/lib/moo.h
index db54bf5..9997d85 100644
--- a/moo/lib/moo.h
+++ b/moo/lib/moo.h
@@ -1,7 +1,7 @@
 /*
  * $Id$
  *
-    Copyright (c) 2014-2017 Chung, Hyung-Hwan. All rights reserved.
+    Copyright (c) 2014-2018 Chung, Hyung-Hwan. All rights reserved.
 
     Redistribution and use in source and binary forms, with or without
     modification, are permitted provided that the following conditions
diff --git a/moo/lib/obj.c b/moo/lib/obj.c
index 0d2fbe6..ff805b2 100644
--- a/moo/lib/obj.c
+++ b/moo/lib/obj.c
@@ -1,7 +1,7 @@
 /*
  * $Id$
  *
-    Copyright (c) 2014-2017 Chung, Hyung-Hwan. All rights reserved.
+    Copyright (c) 2014-2018 Chung, Hyung-Hwan. All rights reserved.
 
     Redistribution and use in source and binary forms, with or without
     modification, are permitted provided that the following conditions
diff --git a/moo/lib/opt-impl.h b/moo/lib/opt-impl.h
index 19e2d1b..c398227 100644
--- a/moo/lib/opt-impl.h
+++ b/moo/lib/opt-impl.h
@@ -1,7 +1,7 @@
 /*
  * $Id$
  *
-    Copyright (c) 2014-2017 Chung, Hyung-Hwan. All rights reserved.
+    Copyright (c) 2014-2018 Chung, Hyung-Hwan. All rights reserved.
 
     Redistribution and use in source and binary forms, with or without
     modification, are permitted provided that the following conditions
diff --git a/moo/lib/opt.c b/moo/lib/opt.c
index d2e2d64..f8497f4 100644
--- a/moo/lib/opt.c
+++ b/moo/lib/opt.c
@@ -1,7 +1,7 @@
 /*
  * $Id$
  *
-    Copyright (c) 2014-2017 Chung, Hyung-Hwan. All rights reserved.
+    Copyright (c) 2014-2018 Chung, Hyung-Hwan. All rights reserved.
 
     Redistribution and use in source and binary forms, with or without
     modification, are permitted provided that the following conditions
diff --git a/moo/lib/pack1.h b/moo/lib/pack1.h
index cbad10a..36f82f0 100644
--- a/moo/lib/pack1.h
+++ b/moo/lib/pack1.h
@@ -1,7 +1,7 @@
 /*
  * $Id$
  *
-    Copyright (c) 2014-2017 Chung, Hyung-Hwan. All rights reserved.
+    Copyright (c) 2014-2018 Chung, Hyung-Hwan. All rights reserved.
 
     Redistribution and use in source and binary forms, with or without
     modification, are permitted provided that the following conditions
diff --git a/moo/lib/pf-basic.c b/moo/lib/pf-basic.c
index 10e3354..e7a386c 100644
--- a/moo/lib/pf-basic.c
+++ b/moo/lib/pf-basic.c
@@ -1,7 +1,7 @@
 /*
  * $Id$
  *
-    Copyright (c) 2014-2017 Chung, Hyung-Hwan. All rights reserved.
+    Copyright (c) 2014-2018 Chung, Hyung-Hwan. All rights reserved.
 
     Redistribution and use in source and binary forms, with or without
     modification, are permitted provided that the following conditions
diff --git a/moo/lib/rbt.c b/moo/lib/rbt.c
index f724a10..83ae026 100644
--- a/moo/lib/rbt.c
+++ b/moo/lib/rbt.c
@@ -1,7 +1,7 @@
 /*
  * $Id$
  *
-    Copyright (c) 2014-2017 Chung, Hyung-Hwan. All rights reserved.
+    Copyright (c) 2014-2018 Chung, Hyung-Hwan. All rights reserved.
 
     Redistribution and use in source and binary forms, with or without
     modification, are permitted provided that the following conditions
diff --git a/moo/lib/sym.c b/moo/lib/sym.c
index c459e46..52245b7 100644
--- a/moo/lib/sym.c
+++ b/moo/lib/sym.c
@@ -1,7 +1,7 @@
 /*
  * $Id$
  *
-    Copyright (c) 2014-2017 Chung, Hyung-Hwan. All rights reserved.
+    Copyright (c) 2014-2018 Chung, Hyung-Hwan. All rights reserved.
 
     Redistribution and use in source and binary forms, with or without
     modification, are permitted provided that the following conditions
diff --git a/moo/lib/unpack.h b/moo/lib/unpack.h
index 5947c15..a87361b 100644
--- a/moo/lib/unpack.h
+++ b/moo/lib/unpack.h
@@ -1,7 +1,7 @@
 /*
  * $Id$
  *
-    Copyright (c) 2014-2017 Chung, Hyung-Hwan. All rights reserved.
+    Copyright (c) 2014-2018 Chung, Hyung-Hwan. All rights reserved.
 
     Redistribution and use in source and binary forms, with or without
     modification, are permitted provided that the following conditions
diff --git a/moo/lib/utf8.c b/moo/lib/utf8.c
index ef1ecfb..f962e8a 100644
--- a/moo/lib/utf8.c
+++ b/moo/lib/utf8.c
@@ -1,7 +1,7 @@
 /*
  * $Id$
  *
-    Copyright (c) 2014-2017 Chung, Hyung-Hwan. All rights reserved.
+    Copyright (c) 2014-2018 Chung, Hyung-Hwan. All rights reserved.
 
     Redistribution and use in source and binary forms, with or without
     modification, are permitted provided that the following conditions
diff --git a/moo/lib/utl.c b/moo/lib/utl.c
index 3c7631b..0eb3381 100644
--- a/moo/lib/utl.c
+++ b/moo/lib/utl.c
@@ -1,7 +1,7 @@
 /*
  * $Id$
  *
-    Copyright (c) 2014-2017 Chung, Hyung-Hwan. All rights reserved.
+    Copyright (c) 2014-2018 Chung, Hyung-Hwan. All rights reserved.
 
     Redistribution and use in source and binary forms, with or without
     modification, are permitted provided that the following conditions
diff --git a/moo/mod/_sck.h b/moo/mod/_sck.h
index 90275af..84f73ea 100644
--- a/moo/mod/_sck.h
+++ b/moo/mod/_sck.h
@@ -1,7 +1,7 @@
 /*
  * $Id$
  *
-    Copyright (c) 2014-2017 Chung, Hyung-Hwan. All rights reserved.
+    Copyright (c) 2014-2018 Chung, Hyung-Hwan. All rights reserved.
 
     Redistribution and use in source and binary forms, with or without
     modification, are permitted provided that the following conditions
diff --git a/moo/mod/_x11.h b/moo/mod/_x11.h
index 10f811b..6db8769 100644
--- a/moo/mod/_x11.h
+++ b/moo/mod/_x11.h
@@ -1,7 +1,7 @@
 /*
  * $Id$
  *
-    Copyright (c) 2014-2017 Chung, Hyung-Hwan. All rights reserved.
+    Copyright (c) 2014-2018 Chung, Hyung-Hwan. All rights reserved.
 
     Redistribution and use in source and binary forms, with or without
     modification, are permitted provided that the following conditions
diff --git a/moo/mod/ffi.c b/moo/mod/ffi.c
index dcf048c..9b80d82 100644
--- a/moo/mod/ffi.c
+++ b/moo/mod/ffi.c
@@ -1,7 +1,7 @@
 /*
  * $Id$
  *
-    Copyright (c) 2014-2017 Chung, Hyung-Hwan. All rights reserved.
+    Copyright (c) 2014-2018 Chung, Hyung-Hwan. All rights reserved.
 
     Redistribution and use in source and binary forms, with or without
     modification, are permitted provided that the following conditions
diff --git a/moo/mod/sck-addr.c b/moo/mod/sck-addr.c
index 1d8ce80..9e56b25 100644
--- a/moo/mod/sck-addr.c
+++ b/moo/mod/sck-addr.c
@@ -1,7 +1,7 @@
 /*
  * $Id$
  *
-    Copyright (c) 2014-2017 Chung, Hyung-Hwan. All rights reserved.
+    Copyright (c) 2014-2018 Chung, Hyung-Hwan. All rights reserved.
 
     Redistribution and use in source and binary forms, with or without
     modification, are permitted provided that the following conditions
diff --git a/moo/mod/sck.c b/moo/mod/sck.c
index 7a94803..3ffdf95 100644
--- a/moo/mod/sck.c
+++ b/moo/mod/sck.c
@@ -1,7 +1,7 @@
 /*
  * $Id$
  *
-    Copyright (c) 2014-2017 Chung, Hyung-Hwan. All rights reserved.
+    Copyright (c) 2014-2018 Chung, Hyung-Hwan. All rights reserved.
 
     Redistribution and use in source and binary forms, with or without
     modification, are permitted provided that the following conditions
diff --git a/moo/mod/stdio.c b/moo/mod/stdio.c
index 8e82226..0d97427 100644
--- a/moo/mod/stdio.c
+++ b/moo/mod/stdio.c
@@ -1,7 +1,7 @@
 /*
  * $Id$
  *
-    Copyright (c) 2014-2017 Chung, Hyung-Hwan. All rights reserved.
+    Copyright (c) 2014-2018 Chung, Hyung-Hwan. All rights reserved.
 
     Redistribution and use in source and binary forms, with or without
     modification, are permitted provided that the following conditions
diff --git a/moo/mod/x11.c b/moo/mod/x11.c
index c97d0f3..ff949a5 100644
--- a/moo/mod/x11.c
+++ b/moo/mod/x11.c
@@ -1,7 +1,7 @@
 /*
  * $Id$
  *
-    Copyright (c) 2014-2017 Chung, Hyung-Hwan. All rights reserved.
+    Copyright (c) 2014-2018 Chung, Hyung-Hwan. All rights reserved.
 
     Redistribution and use in source and binary forms, with or without
     modification, are permitted provided that the following conditions
@@ -55,7 +55,7 @@ static XChar2b* uchars_to_xchar2bstr (moo_t* moo, const moo_uch_t* inptr, moo_oo
 		uch = *inptr++;
 
 	#if (MOO_SIZEOF_UCH_T > 2)
-		if (uch > 0xFFFF) uc = 0xFFFD; /* unicode replacement character */
+		if (uch > 0xFFFF) uch = 0xFFFD; /* unicode replacement character */
 	#endif
 
 		outptr->byte1 = (uch >> 8) & 0xFF;