diff --git a/ChangeLog b/ChangeLog
index 1495ed9f1c..2e0aaec6ec 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Sat Dec 18 21:52:37 2010  Kazuhiro NISHIYAMA  <zn@mbf.nifty.com>
+
+	* vsnprintf.c (BSD_vfprintf): suppress warning: "_WIN32" is not
+	  defined.
+
 Sat Dec 18 16:02:27 2010  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* compile.c (setup_args), vm.c (invoke_block_from_c),
diff --git a/vsnprintf.c b/vsnprintf.c
index 196e733985..7576b4c5b4 100644
--- a/vsnprintf.c
+++ b/vsnprintf.c
@@ -758,7 +758,7 @@ reswitch:	switch (ch) {
 			flags |= QUADINT;
 			goto rflag;
 #endif /* _HAVE_SANE_QUAD_ */
-#if _WIN32
+#ifdef _WIN32
 		case 'I':
 			if (*fmt == '3' && *(fmt + 1) == '2') {
 			    fmt += 2;