Index: /trunk/src/VBox/Additions/WINNT/Graphics/Video/mp/wddm/VBoxMPVidPn.cpp
===================================================================
--- /trunk/src/VBox/Additions/WINNT/Graphics/Video/mp/wddm/VBoxMPVidPn.cpp	(revision 51959)
+++ /trunk/src/VBox/Additions/WINNT/Graphics/Video/mp/wddm/VBoxMPVidPn.cpp	(revision 51960)
@@ -2236,9 +2236,10 @@
 
 #ifdef VBOX_WDDM_WIN8
+    Assert(!g_VBoxDisplayOnly || !pAllocation);
     if (!g_VBoxDisplayOnly)
+#endif
+    {
         vboxWddmAssignPrimary(pSource, pAllocation, VidPnSourceId);
-    else
-        Assert(!pAllocation);
-#endif
+    }
 
     Assert(pSource->AllocData.SurfDesc.VidPnSourceId == VidPnSourceId);