diff --git a/OvmfPkg/Include/Protocol/XenBus.h b/OvmfPkg/Include/Protocol/XenBus.h
index 4c1247bc93..3509691e03 100644
--- a/OvmfPkg/Include/Protocol/XenBus.h
+++ b/OvmfPkg/Include/Protocol/XenBus.h
@@ -39,7 +39,7 @@ typedef struct
   UINT32 Id;
 } XENSTORE_TRANSACTION;
 
-#define XST_NIL ((XENSTORE_TRANSACTION) { 0 })
+#define XST_NIL ((XENSTORE_TRANSACTION *) NULL)
 
 typedef enum {
   XENSTORE_STATUS_SUCCESS = 0,
@@ -88,7 +88,7 @@ typedef
 XENSTORE_STATUS
 (EFIAPI *XENBUS_XS_READ)(
   IN  XENBUS_PROTOCOL       *This,
-  IN  XENSTORE_TRANSACTION  Transaction,
+  IN  CONST XENSTORE_TRANSACTION *Transaction,
   IN  CONST CHAR8           *Node,
   OUT VOID                  **Result
   );
@@ -112,7 +112,7 @@ typedef
 XENSTORE_STATUS
 (EFIAPI *XENBUS_XS_BACKEND_READ)(
   IN  XENBUS_PROTOCOL       *This,
-  IN  XENSTORE_TRANSACTION  Transaction,
+  IN  CONST XENSTORE_TRANSACTION *Transaction,
   IN  CONST CHAR8           *Node,
   OUT VOID                  **Result
   );
@@ -134,7 +134,7 @@ typedef
 XENSTORE_STATUS
 (EFIAPI *XENBUS_XS_PRINTF) (
   IN XENBUS_PROTOCOL        *This,
-  IN XENSTORE_TRANSACTION   Transaction,
+  IN CONST XENSTORE_TRANSACTION *Transaction,
   IN CONST CHAR8            *Directory,
   IN CONST CHAR8            *Node,
   IN CONST CHAR8            *Format,
@@ -156,7 +156,7 @@ typedef
 XENSTORE_STATUS
 (EFIAPI *XENBUS_XS_REMOVE) (
   IN XENBUS_PROTOCOL        *This,
-  IN XENSTORE_TRANSACTION   Transaction,
+  IN CONST XENSTORE_TRANSACTION *Transaction,
   IN CONST CHAR8            *Node
   );
 
@@ -195,7 +195,7 @@ typedef
 XENSTORE_STATUS
 (EFIAPI *XENBUS_XS_TRANSACTION_END) (
   IN XENBUS_PROTOCOL        *This,
-  IN XENSTORE_TRANSACTION   Transaction,
+  IN CONST XENSTORE_TRANSACTION *Transaction,
   IN BOOLEAN                Abort
   );
 
@@ -213,7 +213,7 @@ typedef
 XENSTORE_STATUS
 (EFIAPI *XENBUS_SET_STATE)(
   IN XENBUS_PROTOCOL        *This,
-  IN XENSTORE_TRANSACTION   Transaction,
+  IN CONST XENSTORE_TRANSACTION *Transaction,
   IN XenBusState            State
   );
 
diff --git a/OvmfPkg/XenBusDxe/XenBus.c b/OvmfPkg/XenBusDxe/XenBus.c
index 896a6607b7..a569cfa088 100644
--- a/OvmfPkg/XenBusDxe/XenBus.c
+++ b/OvmfPkg/XenBusDxe/XenBus.c
@@ -314,7 +314,7 @@ XENSTORE_STATUS
 EFIAPI
 XenBusSetState (
   IN XENBUS_PROTOCOL      *This,
-  IN XENSTORE_TRANSACTION Transaction,
+  IN CONST XENSTORE_TRANSACTION *Transaction,
   IN enum xenbus_state    NewState
   )
 {
diff --git a/OvmfPkg/XenBusDxe/XenStore.c b/OvmfPkg/XenBusDxe/XenStore.c
index aed6b141bd..f176b95a4d 100644
--- a/OvmfPkg/XenBusDxe/XenStore.c
+++ b/OvmfPkg/XenBusDxe/XenStore.c
@@ -790,7 +790,7 @@ XenStoreReadReply (
 STATIC
 XENSTORE_STATUS
 XenStoreTalkv (
-  IN  XENSTORE_TRANSACTION    Transaction,
+  IN  CONST XENSTORE_TRANSACTION *Transaction,
   IN  enum xsd_sockmsg_type   RequestType,
   IN  CONST WRITE_REQUEST     *WriteRequest,
   IN  UINT32                  NumRequests,
@@ -803,7 +803,11 @@ XenStoreTalkv (
   UINT32 Index;
   XENSTORE_STATUS Status;
 
-  Message.tx_id = Transaction.Id;
+  if (Transaction == XST_NIL) {
+    Message.tx_id = 0;
+  } else {
+    Message.tx_id = Transaction->Id;
+  }
   Message.req_id = 0;
   Message.type = RequestType;
   Message.len = 0;
@@ -869,7 +873,7 @@ Error:
 STATIC
 XENSTORE_STATUS
 XenStoreSingle (
-  IN  XENSTORE_TRANSACTION    Transaction,
+  IN  CONST XENSTORE_TRANSACTION *Transaction,
   IN  enum xsd_sockmsg_type   RequestType,
   IN  CONST CHAR8             *Body,
   OUT UINT32                  *LenPtr OPTIONAL,
@@ -1157,7 +1161,7 @@ XenStoreDeinit (
 
 XENSTORE_STATUS
 XenStoreListDirectory (
-  IN  XENSTORE_TRANSACTION  Transaction,
+  IN  CONST XENSTORE_TRANSACTION *Transaction,
   IN  CONST CHAR8           *DirectoryPath,
   IN  CONST CHAR8           *Node,
   OUT UINT32                *DirectoryCountPtr,
@@ -1184,7 +1188,7 @@ XenStoreListDirectory (
 
 BOOLEAN
 XenStorePathExists (
-  IN XENSTORE_TRANSACTION  Transaction,
+  IN CONST XENSTORE_TRANSACTION *Transaction,
   IN CONST CHAR8           *Directory,
   IN CONST CHAR8           *Node
   )
@@ -1204,7 +1208,7 @@ XenStorePathExists (
 
 XENSTORE_STATUS
 XenStoreRead (
-  IN  XENSTORE_TRANSACTION    Transaction,
+  IN  CONST XENSTORE_TRANSACTION *Transaction,
   IN  CONST CHAR8             *DirectoryPath,
   IN  CONST CHAR8             *Node,
   OUT UINT32                  *LenPtr OPTIONAL,
@@ -1228,7 +1232,7 @@ XenStoreRead (
 
 XENSTORE_STATUS
 XenStoreWrite (
-  IN XENSTORE_TRANSACTION  Transaction,
+  IN CONST XENSTORE_TRANSACTION *Transaction,
   IN CONST CHAR8           *DirectoryPath,
   IN CONST CHAR8           *Node,
   IN CONST CHAR8           *Str
@@ -1253,7 +1257,7 @@ XenStoreWrite (
 
 XENSTORE_STATUS
 XenStoreRemove (
-  IN XENSTORE_TRANSACTION   Transaction,
+  IN CONST XENSTORE_TRANSACTION *Transaction,
   IN CONST CHAR8            *DirectoryPath,
   IN CONST CHAR8            *Node
   )
@@ -1288,7 +1292,7 @@ XenStoreTransactionStart (
 
 XENSTORE_STATUS
 XenStoreTransactionEnd (
-  IN XENSTORE_TRANSACTION   Transaction,
+  IN CONST XENSTORE_TRANSACTION *Transaction,
   IN BOOLEAN                Abort
   )
 {
@@ -1305,7 +1309,7 @@ XenStoreTransactionEnd (
 
 XENSTORE_STATUS
 XenStoreVSPrint (
-  IN XENSTORE_TRANSACTION  Transaction,
+  IN CONST XENSTORE_TRANSACTION *Transaction,
   IN CONST CHAR8           *DirectoryPath,
   IN CONST CHAR8           *Node,
   IN CONST CHAR8           *FormatString,
@@ -1328,7 +1332,7 @@ XenStoreVSPrint (
 XENSTORE_STATUS
 EFIAPI
 XenStoreSPrint (
-  IN XENSTORE_TRANSACTION   Transaction,
+  IN CONST XENSTORE_TRANSACTION *Transaction,
   IN CONST CHAR8            *DirectoryPath,
   IN CONST CHAR8            *Node,
   IN CONST CHAR8            *FormatString,
@@ -1444,7 +1448,7 @@ XENSTORE_STATUS
 EFIAPI
 XenBusXenStoreRead (
   IN  XENBUS_PROTOCOL       *This,
-  IN  XENSTORE_TRANSACTION  Transaction,
+  IN  CONST XENSTORE_TRANSACTION *Transaction,
   IN  CONST CHAR8           *Node,
   OUT VOID                  **Value
   )
@@ -1456,7 +1460,7 @@ XENSTORE_STATUS
 EFIAPI
 XenBusXenStoreBackendRead (
   IN  XENBUS_PROTOCOL       *This,
-  IN  XENSTORE_TRANSACTION  Transaction,
+  IN  CONST XENSTORE_TRANSACTION *Transaction,
   IN  CONST CHAR8           *Node,
   OUT VOID                  **Value
   )
@@ -1468,7 +1472,7 @@ XENSTORE_STATUS
 EFIAPI
 XenBusXenStoreRemove (
   IN XENBUS_PROTOCOL        *This,
-  IN XENSTORE_TRANSACTION   Transaction,
+  IN CONST XENSTORE_TRANSACTION *Transaction,
   IN const char             *Node
   )
 {
@@ -1489,7 +1493,7 @@ XENSTORE_STATUS
 EFIAPI
 XenBusXenStoreTransactionEnd (
   IN XENBUS_PROTOCOL        *This,
-  IN XENSTORE_TRANSACTION   Transaction,
+  IN CONST XENSTORE_TRANSACTION *Transaction,
   IN BOOLEAN                Abort
   )
 {
@@ -1500,7 +1504,7 @@ XENSTORE_STATUS
 EFIAPI
 XenBusXenStoreSPrint (
   IN XENBUS_PROTOCOL        *This,
-  IN XENSTORE_TRANSACTION   Transaction,
+  IN CONST XENSTORE_TRANSACTION *Transaction,
   IN CONST CHAR8            *DirectoryPath,
   IN CONST CHAR8            *Node,
   IN CONST CHAR8            *FormatString,
diff --git a/OvmfPkg/XenBusDxe/XenStore.h b/OvmfPkg/XenBusDxe/XenStore.h
index 9020411f6a..de5690119e 100644
--- a/OvmfPkg/XenBusDxe/XenStore.h
+++ b/OvmfPkg/XenBusDxe/XenStore.h
@@ -54,7 +54,7 @@ typedef struct _XENSTORE_WATCH XENSTORE_WATCH;
 **/
 XENSTORE_STATUS
 XenStoreListDirectory (
-  IN  XENSTORE_TRANSACTION  Transaction,
+  IN  CONST XENSTORE_TRANSACTION *Transaction,
   IN  CONST CHAR8           *DirectoryPath,
   IN  CONST CHAR8           *Node,
   OUT UINT32                *DirectoryCountPtr,
@@ -74,7 +74,7 @@ XenStoreListDirectory (
 **/
 BOOLEAN
 XenStorePathExists (
-  IN XENSTORE_TRANSACTION  Transaction,
+  IN CONST XENSTORE_TRANSACTION *Transaction,
   IN CONST CHAR8 *Directory,
   IN CONST CHAR8 *Node
   );
@@ -98,7 +98,7 @@ XenStorePathExists (
 **/
 XENSTORE_STATUS
 XenStoreRead (
-  IN  XENSTORE_TRANSACTION    Transaction,
+  IN  CONST XENSTORE_TRANSACTION *Transaction,
   IN  CONST CHAR8             *DirectoryPath,
   IN  CONST CHAR8             *Node,
   OUT UINT32                  *LenPtr OPTIONAL,
@@ -118,7 +118,7 @@ XenStoreRead (
 **/
 XENSTORE_STATUS
 XenStoreWrite (
-  IN XENSTORE_TRANSACTION  Transaction,
+  IN CONST XENSTORE_TRANSACTION *Transaction,
   IN CONST CHAR8           *DirectoryPath,
   IN CONST CHAR8           *Node,
   IN CONST CHAR8           *Str
@@ -136,7 +136,7 @@ XenStoreWrite (
 **/
 XENSTORE_STATUS
 XenStoreRemove (
-  IN XENSTORE_TRANSACTION   Transaction,
+  IN CONST XENSTORE_TRANSACTION *Transaction,
   IN CONST CHAR8            *DirectoryPath,
   IN CONST CHAR8            *Node
   );
@@ -155,7 +155,7 @@ XenStoreRemove (
 **/
 XENSTORE_STATUS
 XenStoreTransactionStart (
-  OUT XENSTORE_TRANSACTION  *Transaction
+  OUT XENSTORE_TRANSACTION *Transaction
   );
 
 /**
@@ -170,7 +170,7 @@ XenStoreTransactionStart (
 **/
 XENSTORE_STATUS
 XenStoreTransactionEnd (
-  IN XENSTORE_TRANSACTION   Transaction,
+  IN CONST XENSTORE_TRANSACTION *Transaction,
   IN BOOLEAN                Abort
   );
 
@@ -189,7 +189,7 @@ XenStoreTransactionEnd (
 XENSTORE_STATUS
 EFIAPI
 XenStoreSPrint (
-  IN XENSTORE_TRANSACTION   Transaction,
+  IN CONST XENSTORE_TRANSACTION *Transaction,
   IN CONST CHAR8            *DirectoryPath,
   IN CONST CHAR8            *Node,
   IN CONST CHAR8            *FormatString,
@@ -210,7 +210,7 @@ XenStoreSPrint (
 **/
 XENSTORE_STATUS
 XenStoreVSPrint (
-  IN XENSTORE_TRANSACTION  Transaction,
+  IN CONST XENSTORE_TRANSACTION *Transaction,
   IN CONST CHAR8           *DirectoryPath,
   IN CONST CHAR8           *Node,
   IN CONST CHAR8           *FormatString,
@@ -305,7 +305,7 @@ XENSTORE_STATUS
 EFIAPI
 XenBusXenStoreRead (
   IN  XENBUS_PROTOCOL       *This,
-  IN  XENSTORE_TRANSACTION  Transaction,
+  IN  CONST XENSTORE_TRANSACTION *Transaction,
   IN  CONST CHAR8           *Node,
   OUT VOID                  **Value
   );
@@ -314,7 +314,7 @@ XENSTORE_STATUS
 EFIAPI
 XenBusXenStoreBackendRead (
   IN  XENBUS_PROTOCOL       *This,
-  IN  XENSTORE_TRANSACTION  Transaction,
+  IN  CONST XENSTORE_TRANSACTION *Transaction,
   IN  CONST CHAR8           *Node,
   OUT VOID                  **Value
   );
@@ -323,7 +323,7 @@ XENSTORE_STATUS
 EFIAPI
 XenBusXenStoreRemove (
   IN XENBUS_PROTOCOL        *This,
-  IN XENSTORE_TRANSACTION   Transaction,
+  IN CONST XENSTORE_TRANSACTION *Transaction,
   IN CONST CHAR8            *Node
   );
 
@@ -338,7 +338,7 @@ XENSTORE_STATUS
 EFIAPI
 XenBusXenStoreTransactionEnd (
   IN XENBUS_PROTOCOL        *This,
-  IN XENSTORE_TRANSACTION   Transaction,
+  IN CONST XENSTORE_TRANSACTION *Transaction,
   IN BOOLEAN                Abort
   );
 
@@ -346,7 +346,7 @@ XENSTORE_STATUS
 EFIAPI
 XenBusXenStoreSPrint (
   IN XENBUS_PROTOCOL        *This,
-  IN XENSTORE_TRANSACTION   Transaction,
+  IN CONST XENSTORE_TRANSACTION *Transaction,
   IN CONST CHAR8            *DirectoryPath,
   IN CONST CHAR8            *Node,
   IN CONST CHAR8            *FormatString,
diff --git a/OvmfPkg/XenPvBlkDxe/BlockFront.c b/OvmfPkg/XenPvBlkDxe/BlockFront.c
index 3c039e7add..8d43d833b0 100644
--- a/OvmfPkg/XenPvBlkDxe/BlockFront.c
+++ b/OvmfPkg/XenPvBlkDxe/BlockFront.c
@@ -166,7 +166,7 @@ XenPvBlockFrontInitialization (
   OUT XEN_BLOCK_FRONT_DEVICE  **DevPtr
   )
 {
-  XENSTORE_TRANSACTION xbt;
+  XENSTORE_TRANSACTION Transaction;
   CHAR8 *DeviceType;
   blkif_sring_t *SharedRing;
   XENSTORE_STATUS Status;
@@ -209,38 +209,38 @@ XenPvBlockFrontInitialization (
                          &Dev->RingRef);
 
 Again:
-  Status = XenBusIo->XsTransactionStart (XenBusIo, &xbt);
+  Status = XenBusIo->XsTransactionStart (XenBusIo, &Transaction);
   if (Status != XENSTORE_STATUS_SUCCESS) {
     DEBUG ((EFI_D_WARN, "XenPvBlk: Failed to start transaction, %d\n", Status));
     goto Error;
   }
 
-  Status = XenBusIo->XsPrintf (XenBusIo, xbt, NodeName, "ring-ref", "%d",
+  Status = XenBusIo->XsPrintf (XenBusIo, &Transaction, NodeName, "ring-ref", "%d",
                                Dev->RingRef);
   if (Status != XENSTORE_STATUS_SUCCESS) {
     DEBUG ((EFI_D_ERROR, "XenPvBlk: Failed to write ring-ref.\n"));
     goto AbortTransaction;
   }
-  Status = XenBusIo->XsPrintf (XenBusIo, xbt, NodeName,
+  Status = XenBusIo->XsPrintf (XenBusIo, &Transaction, NodeName,
                                "event-channel", "%d", Dev->EventChannel);
   if (Status != XENSTORE_STATUS_SUCCESS) {
     DEBUG ((EFI_D_ERROR, "XenPvBlk: Failed to write event-channel.\n"));
     goto AbortTransaction;
   }
-  Status = XenBusIo->XsPrintf (XenBusIo, xbt, NodeName,
+  Status = XenBusIo->XsPrintf (XenBusIo, &Transaction, NodeName,
                                "protocol", "%a", XEN_IO_PROTO_ABI_NATIVE);
   if (Status != XENSTORE_STATUS_SUCCESS) {
     DEBUG ((EFI_D_ERROR, "XenPvBlk: Failed to write protocol.\n"));
     goto AbortTransaction;
   }
 
-  Status = XenBusIo->SetState (XenBusIo, xbt, XenbusStateConnected);
+  Status = XenBusIo->SetState (XenBusIo, &Transaction, XenbusStateConnected);
   if (Status != XENSTORE_STATUS_SUCCESS) {
     DEBUG ((EFI_D_ERROR, "XenPvBlk: Failed to switch state.\n"));
     goto AbortTransaction;
   }
 
-  Status = XenBusIo->XsTransactionEnd (XenBusIo, xbt, FALSE);
+  Status = XenBusIo->XsTransactionEnd (XenBusIo, &Transaction, FALSE);
   if (Status == XENSTORE_STATUS_EAGAIN) {
     goto Again;
   }
@@ -319,7 +319,7 @@ Error2:
   XenBusIo->XsRemove (XenBusIo, XST_NIL, "protocol");
   goto Error;
 AbortTransaction:
-  XenBusIo->XsTransactionEnd (XenBusIo, xbt, TRUE);
+  XenBusIo->XsTransactionEnd (XenBusIo, &Transaction, TRUE);
 Error:
   XenPvBlockFree (Dev);
   return EFI_DEVICE_ERROR;