diff --git a/ncurses/widechar/charable.c b/ncurses/widechar/charable.c
index 91ceb32..55d4890 100644
--- a/ncurses/widechar/charable.c
+++ b/ncurses/widechar/charable.c
@@ -1,5 +1,6 @@
 /****************************************************************************
- * Copyright (c) 2003-2005,2008 Free Software Foundation, Inc.              *
+ * Copyright 2018,2020 Thomas E. Dickey                                     *
+ * Copyright 2003-2005,2008 Free Software Foundation, Inc.                  *
  *                                                                          *
  * Permission is hereby granted, free of charge, to any person obtaining a  *
  * copy of this software and associated documentation files (the            *
@@ -32,7 +33,7 @@
 
 #include <curses.priv.h>
 
-MODULE_ID("$Id: charable.c,v 1.5 2008/07/05 20:51:41 tom Exp $")
+MODULE_ID("$Id: charable.c,v 1.8 2020/02/02 23:34:34 tom Exp $")
 
 NCURSES_EXPORT(bool) _nc_is_charable(wchar_t ch)
 {
@@ -57,6 +58,8 @@
 	result = UChar(temp[0]);
     else
 	result = -1;
+#else
+#error expected either wctob/wctomb
 #endif
     return result;
 }
@@ -75,6 +78,8 @@
 	result = convert;
     else
 	result = WEOF;
+#else
+#error expected either btowc/mbtowc
 #endif
     return result;
 }