Index: /trunk/src/VBox/Devices/Storage/VBoxSCSI.cpp
===================================================================
--- /trunk/src/VBox/Devices/Storage/VBoxSCSI.cpp	(revision 40675)
+++ /trunk/src/VBox/Devices/Storage/VBoxSCSI.cpp	(revision 40676)
@@ -346,5 +346,8 @@
     /* Read string only valid for data in register. */
     AssertMsg(iRegister == 1, ("Hey only register 1 can be read from with string\n"));
-    Assert(pVBoxSCSI->pBuf);
+
+    /* Accesses without a valid buffer will be ignored. */
+    if (!pVBoxSCSI->pBuf)
+        return VINF_SUCCESS;
 
     int rc = PGMPhysSimpleDirtyWriteGCPtr(PDMDevHlpGetVMCPU(pDevIns), GCDst, pVBoxSCSI->pBuf, cbTransfer);
@@ -375,4 +378,9 @@
     /* Write string only valid for data in/out register. */
     AssertMsg(iRegister == 1, ("Hey only register 1 can be written to with string\n"));
+
+    /* Accesses without a valid buffer will be ignored. */
+    if (!pVBoxSCSI->pBuf)
+        return VINF_SUCCESS;
+
     Assert(cbTransfer == pVBoxSCSI->cbBuf);
     if (cbTransfer > pVBoxSCSI->cbBuf)