diff --git a/ChangeLog b/ChangeLog
index e4700a064a..7f7c769d0d 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Fri Jul  8 15:01:06 2011  NAKAMURA Usaku  <usa@ruby-lang.org>
+
+	* ext/openssl/ossl.h: include openssl/e_os2.h before checking the
+	  defition of OPENSSL_SYS_WIN32.
+
 Fri Jul  8 14:40:39 2011  NAKAMURA Usaku  <usa@ruby-lang.org>
 
 	* win32/win32.c (wunlink): reverted a part of r32426. it was mistakenly
diff --git a/ext/openssl/ossl.h b/ext/openssl/ossl.h
index c97dc5ac51..97095f7d6f 100644
--- a/ext/openssl/ossl.h
+++ b/ext/openssl/ossl.h
@@ -45,6 +45,7 @@ extern "C" {
 #endif
 
 #if defined(_WIN32)
+#  include <openssl/e_os2.h>
 #  define OSSL_NO_CONF_API 1
 #  if !defined(OPENSSL_SYS_WIN32)
 #    define OPENSSL_SYS_WIN32 1