diff --git a/ChangeLog b/ChangeLog
index 71ece1b2725919aaa583262391b26144fcd4f43b..2a3da4c126d048a33a54a4e0e06b915512da8187 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -250,7 +250,7 @@ CVS code -
 	  Weinehall)
 	- Don't refer to the built-in file browser as crappy anymore.
 	  (DLR)
-	- Check for iswpunct(). (DLR)
+	- Check for iswpunct() and mbstowcs(). (DLR)
 - doc/faq.html:
 	- Update the question about the FAQ to mention the current
 	  maintainer. (DLR)
diff --git a/configure.ac b/configure.ac
index ccbc9c36378d5cc911b7dc499c8a7daec91c72f1..2df63185c71003fb96b8e06cabeec221dc28ebb7 100644
--- a/configure.ac
+++ b/configure.ac
@@ -399,7 +399,7 @@ dnl Checks for functions.
 AC_CHECK_FUNCS(snprintf vsnprintf isblank strcasecmp strncasecmp strcasestr strnlen getline getdelim)
 
 if test x$enable_utf8 != xno; then
-    AC_CHECK_FUNCS(iswalnum iswblank iswpunct iswspace mblen mbtowc wctomb wcwidth)
+    AC_CHECK_FUNCS(iswalnum iswblank iswpunct iswspace mblen mbstowcs mbtowc wctomb wcwidth)
 fi
 
 if test x$ac_cv_func_snprintf = xno || test x$ac_cv_func_vsnprintf = xno; then
@@ -475,10 +475,11 @@ if test x$enable_utf8 != xno && \
    test x$ac_cv_func_iswpunct = xyes && \
    (test x$ac_cv_func_iswblank = xyes || test x$ac_cv_func_iswspace = xyes) && \
    test x$ac_cv_func_mblen = xyes && \
+   test x$ac_cv_func_mbstowcs = xyes && \
    test x$ac_cv_func_mbtowc = xyes && \
    test x$ac_cv_func_wctomb = xyes && \
    test x$ac_cv_func_wcwidth = xyes; then
-	AC_DEFINE(NANO_WIDE, 1, [Define this if your system has sufficient wide character support (a wide curses library, iswalnum(), iswpunct(), iswblank() or iswspace(), mblen(), mbtowc(), wctomb(), and wcwidth()).])
+	AC_DEFINE(NANO_WIDE, 1, [Define this if your system has sufficient wide character support (a wide curses library, iswalnum(), iswpunct(), iswblank() or iswspace(), mblen(), mbstowcs(), mbtowc(), wctomb(), and wcwidth()).])
 else
     if test x$enable_utf8 = xyes; then
 	AC_MSG_ERROR([
diff --git a/src/chars.c b/src/chars.c
index bd2f0d577b8ffbae9f0009ef2ae6cbb4dbb5b7be..34712dc75140d1331a7eb9f9a7fd5ea2f66092ae 100644
--- a/src/chars.c
+++ b/src/chars.c
@@ -285,23 +285,13 @@ bool is_valid_mbstring(const char *str)
 {
     assert(str != NULL);
 
+    return 
 #ifdef NANO_WIDE
-    if (!ISSET(NO_UTF8)) {
-	while (*str != '\0') {
-	    int chr_mb_len;
-	    bool bad_chr;
-
-	    chr_mb_len = parse_mbchar(str, NULL, &bad_chr, NULL);
-
-	    if (bad_chr)
-		return FALSE;
-
-	    str += chr_mb_len;
-	}
-     }
+	(!ISSET(NO_UTF8)) ?
+	(mbstowcs(NULL, str, (size_t)-1) != (size_t)-1) :
 #endif
 
-     return TRUE;
+	TRUE;
 }
 #endif /* ENABLE_NANORC */