--- ./src/regression/mbsnrtowcs-overread.c	1970-01-01 03:00:00.000000000 +0300
+++ ./src/regression/mbsnrtowcs-overread.c	2017-08-09 20:20:29.472003066 +0300
@@ -0,0 +1,45 @@
+// mbsnrtowcs issue, reported in www.openwall.com/lists/musl/2017/07/18/3
+#include <locale.h>
+#include <stdio.h>
+#include <string.h>
+#include <wchar.h>
+#include "test.h"
+
+int main(void)
+{
+	const char *const chr = "\u044B";
+	const int chr_size = strlen(chr);
+	// The passed length of the source string in bytes should be bigger than
+	// 32*4 to force mbsnrtowcs to use the optimization based on mbsrtowcs.
+	const int chr_count_to_convert = 1000;
+	// Make sure that the source string has more characters after the passed
+	// length.
+	const int chr_count = chr_count_to_convert + 10;
+	
+	char src[chr_count * chr_size + 1];
+	// dest should also have extra space
+	wchar_t dest[chr_count + 1];
+	size_t r;
+	const char *str_ptr = src;
+	mbstate_t mbs;
+
+	for (int i = 0; i < chr_count; ++i)
+	{
+		memcpy(src + i * chr_size, chr, chr_size);
+	}
+	src[chr_count * chr_size] = 0;
+ 
+	setlocale(LC_CTYPE, "en_US.UTF-8");
+
+	memset(&mbs, 0, sizeof(mbs));
+	r = mbsnrtowcs(dest, &str_ptr, chr_count_to_convert * chr_size,
+	               sizeof(dest)/sizeof(dest[0]), &mbs);
+
+	if (r != chr_count_to_convert)
+	{
+		t_error("Expected to convert %d characters, but converted %d\n",
+			chr_count_to_convert, r);
+	}
+
+	return t_status;
+}
--- ./src/regression/wcsnrtombs_underread.c	1970-01-01 03:00:00.000000000 +0300
+++ ./src/regression/wcsnrtombs_underread.c	2017-08-09 20:24:57.575995227 +0300
@@ -0,0 +1,46 @@
+// wcsnrtombs issue, reported in www.openwall.com/lists/musl/2017/07/18/3
+#include <locale.h>
+#include <stdio.h>
+#include <string.h>
+#include <wchar.h>
+#include "test.h"
+
+#define TEST_CHR "\u044B"
+
+#define CAT_IMPL(x, y) x##y
+#define CAT(x, y) CAT_IMPL(x, y)
+
+int main(void)
+{
+	const wchar_t *const chr = CAT(L, TEST_CHR);
+	const int chr_len_in_utf_8 = strlen(TEST_CHR);
+	const int chr_size = wcslen(chr);
+	// The number of characters should be greater than 32 to force wcsnrtombs
+	// to use the optimization based on wcsrtombs.
+	const int chr_count = 1000;
+	wchar_t src[chr_count];
+	char dest[chr_count * 4];
+	size_t r;
+	const wchar_t *str_ptr = src;
+	mbstate_t mbs;
+
+	for (int i = 0; i < chr_count; ++i)
+	{
+		memcpy(src + i, chr, sizeof(*chr));
+	}
+	src[chr_count] = 0;
+
+	setlocale(LC_CTYPE, "en_US.UTF-8");
+
+	memset(&mbs, 0, sizeof(mbs));
+	r = wcsnrtombs(dest, &str_ptr, chr_count,
+				   sizeof(dest), &mbs);
+
+	if (r != chr_count * chr_len_in_utf_8)
+	{
+		t_error("Expected to fill %d bytes, but filled %d\n",
+			chr_count * chr_len_in_utf_8, r);
+	}
+
+	return t_status;
+}