diff --git a/MdePkg/Include/Protocol/PciIo.h b/MdePkg/Include/Protocol/PciIo.h
index 42bcc81830..d6492fcf04 100644
--- a/MdePkg/Include/Protocol/PciIo.h
+++ b/MdePkg/Include/Protocol/PciIo.h
@@ -331,7 +331,7 @@ EFI_STATUS
 
 /**                                                                 
   Allocates pages that are suitable for an EfiPciIoOperationBusMasterCommonBuffer
-  mapping.                                                                       
+  or EfiPciOperationBusMasterCommonBuffer64 mapping.
             
   @param  This                  A pointer to the EFI_PCI_IO_PROTOCOL instance.
   @param  Type                  This parameter is not used and must be ignored.
@@ -344,7 +344,7 @@ EFI_STATUS
                                   
   @retval EFI_SUCCESS           The requested memory pages were allocated.
   @retval EFI_UNSUPPORTED       Attributes is unsupported. The only legal attribute bits are
-                                MEMORY_WRITE_COMBINE and MEMORY_CACHED.                     
+                                MEMORY_WRITE_COMBINE, MEMORY_CACHED and DUAL_ADDRESS_CYCLE.
   @retval EFI_INVALID_PARAMETER One or more parameters are invalid.
   @retval EFI_OUT_OF_RESOURCES  The memory pages could not be allocated.