diff --git a/ChangeLog b/ChangeLog
index f859ca0462..64bf871d9b 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,4 +1,7 @@
-Wed Nov 28 21:21:16 2012  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+Wed Nov 28 21:22:44 2012  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* ext/psych/extconf.rb: mingw32 also needs macros for win32, not
+	  only mswin32.
 
 	* ext/psych/extconf.rb: compile sources in the source directory
 	  without copying by using VPATH.
diff --git a/ext/psych/extconf.rb b/ext/psych/extconf.rb
index c545a9de77..bba3ab2c63 100644
--- a/ext/psych/extconf.rb
+++ b/ext/psych/extconf.rb
@@ -1,3 +1,4 @@
+# -*- coding: us-ascii -*-
 require 'mkmf'
 require 'fileutils'
 
@@ -13,8 +14,8 @@ unless find_header('yaml.h') && find_library('yaml', 'yaml_get_version')
 
   $srcs = Dir.glob("#{$srcdir}/{,yaml/}*.c").map {|n| File.basename(n)}
 
-  if $mswin
-    $CFLAGS += " -DYAML_DECLARE_STATIC -DHAVE_CONFIG_H"
+  if have_macro("_WIN32")
+    $CPPFLAGS << " -DYAML_DECLARE_STATIC -DHAVE_CONFIG_H"
   end
 
   have_header 'dlfcn.h'