Index: /trunk/src/VBox/Additions/WINNT/Graphics/Video/disp/Makefile.kmk
===================================================================
--- /trunk/src/VBox/Additions/WINNT/Graphics/Video/disp/Makefile.kmk	(revision 42225)
+++ /trunk/src/VBox/Additions/WINNT/Graphics/Video/disp/Makefile.kmk	(revision 42226)
@@ -29,4 +29,5 @@
 VBoxDisp_SDKS          = ReorderCompilerIncs $(VBOX_WINDDK_GST_NT4)
 VBoxDisp_DEFS.x86     = _WIN32_WINNT=0x0501
+VBoxDisp_DEFS.amd64   = _WIN32_WINNT=0x0500 # <- otherwise the build will fail due to DDK header inconsistencies
 VBoxDisp_DEFS          = VBOX_WITH_DDRAW
 VBoxDisp_DEFS         += LOG_TO_BACKDOOR #LOG_ENABLED