diff --git a/intern/ghost/intern/GHOST_SystemWin32.cpp b/intern/ghost/intern/GHOST_SystemWin32.cpp
index 293f8fc1661..f5c7c08ebfe 100644
--- a/intern/ghost/intern/GHOST_SystemWin32.cpp
+++ b/intern/ghost/intern/GHOST_SystemWin32.cpp
@@ -42,6 +42,14 @@
 
 #include "GHOST_SystemWin32.h"
 
+// win64 doesn't define GWL_USERDATA
+#ifdef WIN32
+#ifndef GWL_USERDATA
+#define GWL_USERDATA GWLP_USERDATA
+#define GWL_WNDPROC GWLP_WNDPROC
+#endif
+#endif
+
 /*
  * According to the docs the mouse wheel message is supported from windows 98 
  * upwards. Leaving WINVER at default value, the WM_MOUSEWHEEL message and the 
diff --git a/intern/ghost/intern/GHOST_WindowWin32.cpp b/intern/ghost/intern/GHOST_WindowWin32.cpp
index 905b2f7ac63..fef58d071a4 100644
--- a/intern/ghost/intern/GHOST_WindowWin32.cpp
+++ b/intern/ghost/intern/GHOST_WindowWin32.cpp
@@ -48,6 +48,14 @@
 #define M_PI 3.1415926536
 #endif
 
+// win64 doesn't define GWL_USERDATA
+#ifdef WIN32
+#ifndef GWL_USERDATA
+#define GWL_USERDATA GWLP_USERDATA
+#define GWL_WNDPROC GWLP_WNDPROC
+#endif
+#endif
+
 LPCSTR GHOST_WindowWin32::s_windowClassName = "GHOST_WindowClass";
 const int GHOST_WindowWin32::s_maxTitleLength = 128;
 HGLRC GHOST_WindowWin32::s_firsthGLRc = NULL;