Index: /trunk/src/VBox/Additions/common/VBoxGuest/VBoxGuest-win.cpp
===================================================================
--- /trunk/src/VBox/Additions/common/VBoxGuest/VBoxGuest-win.cpp	(revision 46857)
+++ /trunk/src/VBox/Additions/common/VBoxGuest/VBoxGuest-win.cpp	(revision 46858)
@@ -127,4 +127,7 @@
                 case 2:
                     g_enmVbgdNtVer = VBGDNTVER_WIN8;
+                    break;
+                case 3:
+                    g_enmVbgdNtVer = VBGDNTVER_WIN8_1;
                     break;
                 default:
@@ -1326,4 +1329,5 @@
 
         case VBGDNTVER_WIN8:
+        case VBGDNTVER_WIN8_1:
 #if ARCH_BITS == 64
             enmOsType = VBOXOSTYPE_Win8_x64;
Index: /trunk/src/VBox/Additions/common/VBoxGuest/VBoxGuest-win.h
===================================================================
--- /trunk/src/VBox/Additions/common/VBoxGuest/VBoxGuest-win.h	(revision 46857)
+++ /trunk/src/VBox/Additions/common/VBoxGuest/VBoxGuest-win.h	(revision 46858)
@@ -135,5 +135,6 @@
     VBGDNTVER_WINVISTA,
     VBGDNTVER_WIN7,
-    VBGDNTVER_WIN8
+    VBGDNTVER_WIN8,
+    VBGDNTVER_WIN8_1,
 } VBGDNTVER;
 extern VBGDNTVER g_enmVbgdNtVer;