--- ./src/VBox/Additions/common/VBoxGuestLib/Makefile.kmk.orig	2012-12-27 16:42:00.199621337 +0000
+++ ./src/VBox/Additions/common/VBoxGuestLib/Makefile.kmk	2012-12-27 16:43:06.605220980 +0000
@@ -39,11 +39,13 @@ LIBRARIES += \
 	VBoxGuestR3Lib \
 	VBoxGuestR3LibShared
 ifndef VBOX_ONLY_TESTSUITE
+ifndef VBOX_USE_SYSTEM_XORG_HEADERS
  if1of ($(KBUILD_TARGET), freebsd linux netbsd openbsd)
   LIBRARIES += \
   	VBoxGuestR3LibXFree86
  endif
 endif
+endif
 LIBRARIES.win.amd64 += VBoxGuestR3Lib-x86 VBoxGuestR3LibShared-x86