diff --git a/ChangeLog b/ChangeLog
index 28123d8f7f..2e60021779 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Tue Jun 30 18:38:16 2015  NAKAMURA Usaku  <usa@ruby-lang.org>
+
+	* win32/file.c (rb_freopen): need to terminate by NUL.
+
 Tue Jun 30 17:28:25 2015  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* io.c (rb_io_reopen): freopen(3) with OS encoding path.
diff --git a/win32/file.c b/win32/file.c
index 799810a4ef..99d94fef46 100644
--- a/win32/file.c
+++ b/win32/file.c
@@ -725,11 +725,13 @@ int
 rb_freopen(VALUE fname, const char *mode, FILE *file)
 {
     WCHAR *wname, wmode[4];
+    long len;
     int e = 0, n = MultiByteToWideChar(CP_ACP, 0, mode, -1, NULL, 0);
     if (n > numberof(wmode)) return EINVAL;
     MultiByteToWideChar(CP_ACP, 0, mode, -1, wmode, numberof(wmode));
     wname = rb_w32_mbstr_to_wstr(CP_UTF8, RSTRING_PTR(fname),
-				 rb_long2int(RSTRING_LEN(fname)), NULL);
+				 rb_long2int(RSTRING_LEN(fname)) + 1, &len);
+    wname[len - 1] = L'\0';
     RB_GC_GUARD(fname);
 #if RUBY_MSVCRT_VERSION < 80 && !defined(HAVE__WFREOPEN_S)
     e = _wfreopen(wname, wmode, file) ? 0 : errno;
@@ -737,6 +739,7 @@ rb_freopen(VALUE fname, const char *mode, FILE *file)
     {
 	FILE *newfp = 0;
 	e = _wfreopen_s(&newfp, wname, wmode, file);
+	if (e != 0) cprintf("DEBUG: %d [%ls] [%ls]\n", e, wname, wmode);
     }
 #endif
     xfree(wname);