diff --git a/EdkCompatibilityPkg/Compatibility/DeviceIoToPciRootBridgeIoThunk/DeviceIoToPciRootBridgeIoThunk.c b/EdkCompatibilityPkg/Compatibility/DeviceIoToPciRootBridgeIoThunk/DeviceIoToPciRootBridgeIoThunk.c
index 24acfb3b67..db8b72ed44 100644
--- a/EdkCompatibilityPkg/Compatibility/DeviceIoToPciRootBridgeIoThunk/DeviceIoToPciRootBridgeIoThunk.c
+++ b/EdkCompatibilityPkg/Compatibility/DeviceIoToPciRootBridgeIoThunk/DeviceIoToPciRootBridgeIoThunk.c
@@ -541,7 +541,7 @@ DeviceIoMemRead (
     return EFI_INVALID_PARAMETER;
   }
   if (Width >= MMIO_COPY_UINT8) {
-    Width = Width - MMIO_COPY_UINT8;
+    Width = (EFI_IO_WIDTH) (Width - MMIO_COPY_UINT8);
     Status = Private->PciRootBridgeIo->CopyMem (
                                          Private->PciRootBridgeIo,
                                          (EFI_PCI_ROOT_BRIDGE_IO_PROTOCOL_WIDTH) Width,
@@ -600,7 +600,7 @@ DeviceIoMemWrite (
     return EFI_INVALID_PARAMETER;
   }
   if (Width >= MMIO_COPY_UINT8) {
-    Width = Width - MMIO_COPY_UINT8;
+    Width = (EFI_IO_WIDTH) (Width - MMIO_COPY_UINT8);
     Status = Private->PciRootBridgeIo->CopyMem (
                                          Private->PciRootBridgeIo,
                                          (EFI_PCI_ROOT_BRIDGE_IO_PROTOCOL_WIDTH) Width,