diff --git a/OvmfPkg/AcpiPlatformDxe/Qemu.c b/OvmfPkg/AcpiPlatformDxe/Qemu.c
index 051449d72a..4c88c32ec8 100644
--- a/OvmfPkg/AcpiPlatformDxe/Qemu.c
+++ b/OvmfPkg/AcpiPlatformDxe/Qemu.c
@@ -268,8 +268,8 @@ QemuInstallAcpiSsdtTable (
         *(UINT32*) SsdtPtr = sizeof (*FwData);
         SsdtPtr += 4;
 
-        ASSERT(SsdtPtr - Ssdt == SsdtSize);
-        ((EFI_ACPI_DESCRIPTION_HEADER *) Ssdt)->Length = SsdtSize;
+        ASSERT((UINTN) (SsdtPtr - Ssdt) == SsdtSize);
+        ((EFI_ACPI_DESCRIPTION_HEADER *) Ssdt)->Length = (UINT32) SsdtSize;
         Status = InstallAcpiTable (AcpiProtocol, Ssdt, SsdtSize, TableKey);
       }
 
diff --git a/OvmfPkg/AcpiPlatformDxe/Xen.c b/OvmfPkg/AcpiPlatformDxe/Xen.c
index 02ab8402eb..618ac58b42 100644
--- a/OvmfPkg/AcpiPlatformDxe/Xen.c
+++ b/OvmfPkg/AcpiPlatformDxe/Xen.c
@@ -188,7 +188,7 @@ InstallXenTables (
       CurrentTableEntry = (VOID *) ((UINT8 *) Xsdt +
                             sizeof (EFI_ACPI_DESCRIPTION_HEADER) +
                             Index * sizeof (UINT64));
-      CurrentTablePointer = *(UINT64 *)CurrentTableEntry;
+      CurrentTablePointer = (UINTN) *(UINT64 *)CurrentTableEntry;
       CurrentTable = (EFI_ACPI_DESCRIPTION_HEADER *) CurrentTablePointer;
 
       //