Index: /trunk/src/VBox/Devices/Storage/DevAHCI.cpp
===================================================================
--- /trunk/src/VBox/Devices/Storage/DevAHCI.cpp	(revision 64679)
+++ /trunk/src/VBox/Devices/Storage/DevAHCI.cpp	(revision 64680)
@@ -4673,6 +4673,7 @@
             {
                 AHCIREQ Req;
-                Req.uTag   = idx;
-                Req.fFlags = AHCI_REQ_IS_ON_STACK;
+                Req.uTag    = idx;
+                Req.fFlags  = AHCI_REQ_IS_ON_STACK;
+                Req.fMapped = false;
 
                 bool fContinue = ahciR3CmdPrepare(pAhciPort, &Req);