diff --git a/ChangeLog b/ChangeLog
index 9c870c9714..732371201d 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Fri Jun  6 16:41:45 2008  NAKAMURA Usaku  <usa@ruby-lang.org>
+
+	* include/ruby/win32.h: include ws2tcpip.h. fixed [ruby-Bugs-20528]
+
 Fri Jun  6 15:05:02 2008  Tanaka Akira  <akr@fsij.org>
 
 	* gc.c (count_objects): clear hash after counting objects.
diff --git a/include/ruby/win32.h b/include/ruby/win32.h
index a0acb7fff9..a340586d32 100644
--- a/include/ruby/win32.h
+++ b/include/ruby/win32.h
@@ -28,6 +28,7 @@ extern "C" {
 // #include <stdarg.h> conflict with varargs.h?
 #if !defined(WSAAPI)
 #include <winsock2.h>
+#include <ws2tcpip.h>
 #endif
 
 #define NT 1			/* deprecated */