diff --git a/debug/tst-fortify.c b/debug/tst-fortify.c
index 03c9867714..8e94643bf2 100644
--- a/debug/tst-fortify.c
+++ b/debug/tst-fortify.c
@@ -1478,10 +1478,15 @@ do_test (void)
 	 character which has a multibyte representation which does not
 	 fit.  */
       CHK_FAIL_START
-      char smallbuf[2];
+      char smallbuf[1];
       if (wcrtomb (smallbuf, L'\x100', &s) != 2)
 	FAIL ();
       CHK_FAIL_END
+
+      /* Same input with a large enough buffer and we're good.  */
+      char bigenoughbuf[2];
+      if (wcrtomb (bigenoughbuf, L'\x100', &s) != 2)
+	FAIL ();
 #endif
 
       wchar_t wenough[10];
diff --git a/debug/wcrtomb_chk.c b/debug/wcrtomb_chk.c
index 8b6d026560..28c3ea0d2d 100644
--- a/debug/wcrtomb_chk.c
+++ b/debug/wcrtomb_chk.c
@@ -1,4 +1,5 @@
 /* Copyright (C) 2005-2022 Free Software Foundation, Inc.
+   Copyright The GNU Toolchain Authors.
    This file is part of the GNU C Library.
 
    The GNU C Library is free software; you can redistribute it and/or
@@ -25,10 +26,5 @@
 size_t
 __wcrtomb_chk (char *s, wchar_t wchar, mbstate_t *ps, size_t buflen)
 {
-  /* We do not have to implement the full wctomb semantics since we
-     know that S cannot be NULL when we come here.  */
-  if (buflen < MB_CUR_MAX)
-    __chk_fail ();
-
-  return __wcrtomb (s, wchar, ps);
+  return __wcrtomb_internal (s, wchar, ps, buflen);
 }
diff --git a/include/wchar.h b/include/wchar.h
index 4267985625..db83297bca 100644
--- a/include/wchar.h
+++ b/include/wchar.h
@@ -172,6 +172,10 @@ libc_hidden_proto (__mbrtowc)
 libc_hidden_proto (__mbrlen)
 extern size_t __wcrtomb (char *__restrict __s, wchar_t __wc,
 			 __mbstate_t *__restrict __ps) attribute_hidden;
+extern size_t __wcrtomb_internal (char *__restrict __s, wchar_t __wc,
+				  __mbstate_t *__restrict __ps,
+				  size_t __s_size)
+     attribute_hidden;
 extern size_t __mbsrtowcs (wchar_t *__restrict __dst,
 			   const char **__restrict __src,
 			   size_t __len, __mbstate_t *__restrict __ps)
diff --git a/manual/charset.texi b/manual/charset.texi
index a9b5cb4a37..427db3bc80 100644
--- a/manual/charset.texi
+++ b/manual/charset.texi
@@ -883,11 +883,12 @@ the string @var{s}.  This includes all bytes representing shift
 sequences.
 
 One word about the interface of the function: there is no parameter
-specifying the length of the array @var{s}.  Instead the function
-assumes that there are at least @code{MB_CUR_MAX} bytes available since
-this is the maximum length of any byte sequence representing a single
-character.  So the caller has to make sure that there is enough space
-available, otherwise buffer overruns can occur.
+specifying the length of the array @var{s}, so the caller has to make sure
+that there is enough space available, otherwise buffer overruns can occur.
+This version of @theglibc{} does not assume that @var{s} is at least
+@var{MB_CUR_MAX} bytes long, but programs that need to run on @glibcadj{}
+versions that have this assumption documented in the manual must comply
+with this limit.
 
 @pindex wchar.h
 @code{wcrtomb} was introduced in @w{Amendment 1} to @w{ISO C90} and is
diff --git a/wcsmbs/wcrtomb.c b/wcsmbs/wcrtomb.c
index e17438989f..c0cce3792f 100644
--- a/wcsmbs/wcrtomb.c
+++ b/wcsmbs/wcrtomb.c
@@ -1,4 +1,5 @@
 /* Copyright (C) 1996-2022 Free Software Foundation, Inc.
+   Copyright The GNU Toolchain Authors.
    This file is part of the GNU C Library.
 
    The GNU C Library is free software; you can redistribute it and/or
@@ -20,6 +21,7 @@
 #include <errno.h>
 #include <gconv.h>
 #include <stdlib.h>
+#include <string.h>
 #include <wchar.h>
 #include <wcsmbsload.h>
 
@@ -34,7 +36,7 @@
 static mbstate_t state;
 
 size_t
-__wcrtomb (char *s, wchar_t wc, mbstate_t *ps)
+__wcrtomb_internal (char *s, wchar_t wc, mbstate_t *ps, size_t s_size)
 {
   char buf[MB_LEN_MAX];
   struct __gconv_step_data data;
@@ -52,14 +54,11 @@ __wcrtomb (char *s, wchar_t wc, mbstate_t *ps)
   /* A first special case is if S is NULL.  This means put PS in the
      initial state.  */
   if (s == NULL)
-    {
-      s = buf;
-      wc = L'\0';
-    }
+    wc = L'\0';
 
   /* Tell where we want to have the result.  */
-  data.__outbuf = (unsigned char *) s;
-  data.__outbufend = (unsigned char *) s + MB_CUR_MAX;
+  data.__outbuf = (unsigned char *) buf;
+  data.__outbufend = (unsigned char *) buf + sizeof buf;
 
   /* Get the conversion functions.  */
   fcts = get_gconv_fcts (_NL_CURRENT_DATA (LC_CTYPE));
@@ -101,7 +100,17 @@ __wcrtomb (char *s, wchar_t wc, mbstate_t *ps)
 
   if (status == __GCONV_OK || status == __GCONV_EMPTY_INPUT
       || status == __GCONV_FULL_OUTPUT)
-    result = data.__outbuf - (unsigned char *) s;
+    {
+      result = data.__outbuf - (unsigned char *) buf;
+
+      if (s != NULL)
+	{
+	  if (result > s_size)
+	    __chk_fail ();
+
+	  memcpy (s, buf, result);
+	}
+    }
   else
     {
       result = (size_t) -1;
@@ -110,5 +119,11 @@ __wcrtomb (char *s, wchar_t wc, mbstate_t *ps)
 
   return result;
 }
+
+size_t
+__wcrtomb (char *s, wchar_t wc, mbstate_t *ps)
+{
+  return __wcrtomb_internal (s, wc, ps, (size_t) -1);
+}
 weak_alias (__wcrtomb, wcrtomb)
 libc_hidden_weak (wcrtomb)