diff --git a/ChangeLog b/ChangeLog
index 449728e..7c4d049 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+2016-03-01  Seong Gu Lee <sgleehd@gmail.com>
+
+	* Headers/win32/WIN32Server.h: tweak for compilation on 64bit windows
+
 2015-12-13  Fred Kiefer <FredKiefer@gmx.de>
 
 	* Source/opal/OpalFontInfo.m
diff --git a/Headers/win32/WIN32Server.h b/Headers/win32/WIN32Server.h
index 49eaae2..4c3767e 100644
--- a/Headers/win32/WIN32Server.h
+++ b/Headers/win32/WIN32Server.h
@@ -56,6 +56,12 @@
 #include <config.h>
 #include <windows.h>
 
+/* MINGW64 hack to build */
+#ifdef __MINGW64__
+#undef GWL_USERDATA
+#define GWL_USERDATA GWLP_USERDATA 
+#endif
+
 /*
  This standard windows macros are missing in MinGW.  The definition
  here is almost correct, but will fail for multi monitor systems