Index: /trunk/src/VBox/GuestHost/OpenGL/util/net.c
===================================================================
--- /trunk/src/VBox/GuestHost/OpenGL/util/net.c	(revision 50437)
+++ /trunk/src/VBox/GuestHost/OpenGL/util/net.c	(revision 50438)
@@ -1107,10 +1107,16 @@
             crError( "Can't handle read pixels" );
             return;
+        case CR_MESSAGE_WRITEBACK:
 #ifdef IN_GUEST
-        case CR_MESSAGE_WRITEBACK:
             crNetRecvWriteback( &(pRealMsg->writeback) );
+#else
+            WARN(("CR_MESSAGE_WRITEBACK not expected\n"));
+#endif
             return;
         case CR_MESSAGE_READBACK:
+#ifdef IN_GUEST
             crNetRecvReadback( &(pRealMsg->readback), len );
+#else
+            WARN(("CR_MESSAGE_READBACK not expected\n"));
 #endif
             return;