diff --git a/lib/libc/locale/btowc.c b/lib/libc/locale/btowc.c
index 585abf85f0b9..b0b24f2947b3 100644
--- a/lib/libc/locale/btowc.c
+++ b/lib/libc/locale/btowc.c
@@ -1,45 +1,55 @@
 /*-
- * Copyright (c) 2002 Tim J. Robbins.
+ * Copyright (c) 2002, 2003 Tim J. Robbins.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
  *    documentation and/or other materials provided with the distribution.
  *
  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  */
 
 #include <sys/cdefs.h>
 __FBSDID("$FreeBSD$");
 
-#include <rune.h>
+#include <stdio.h>
+#include <string.h>
 #include <wchar.h>
 
 wint_t
 btowc(int c)
 {
-	rune_t r;
 	char cc;
+	wchar_t wc;
 
 	if (c == EOF)
 		return (WEOF);
 	cc = (char)c;
-	if ((r = sgetrune(&cc, 1, NULL)) == _INVALID_RUNE)
+	/*
+	 * We expect mbrtowc() to return 0 or 1, hence the check for n > 1
+	 * which detects error return values as well as "impossible" byte
+	 * counts.
+	 *
+	 * We pass NULL as the state pointer to mbrtowc() because we don't
+	 * support state-dependent encodings and don't want to waste time
+	 * creating a zeroed mbstate_t that will not be used.
+	 */
+	if (mbrtowc(&wc, &cc, 1, NULL) > 1)
 		return (WEOF);
-	return (r);
+	return (wc);
 }
diff --git a/lib/libc/locale/wctob.c b/lib/libc/locale/wctob.c
index 070ae94ce650..da7afcf44142 100644
--- a/lib/libc/locale/wctob.c
+++ b/lib/libc/locale/wctob.c
@@ -1,41 +1,48 @@
 /*-
- * Copyright (c) 2002 Tim J. Robbins.
+ * Copyright (c) 2002, 2003 Tim J. Robbins.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
  *    documentation and/or other materials provided with the distribution.
  *
  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  */
 
 #include <sys/cdefs.h>
 __FBSDID("$FreeBSD$");
 
-#include <rune.h>
+#include <limits.h>
+#include <stdio.h>
+#include <string.h>
 #include <wchar.h>
 
 int
 wctob(wint_t c)
 {
-	char cc;
+	char buf[MB_LEN_MAX];
 
-	if (c == WEOF || sputrune(c, &cc, 1, NULL) != 1)
+	/*
+	 * We pass NULL as the state pointer to wcrtomb() because we don't
+	 * support state-dependent encodings and don't want to waste time
+	 * creating a zeroed mbstate_t that will not be used.
+	 */
+	if (c == WEOF || wcrtomb(buf, c, NULL) != 1)
 		return (EOF);
-	return ((unsigned char)cc);
+	return ((unsigned char)*buf);
 }