diff --git a/MdePkg/Include/Protocol/StorageSecurityCommand.h b/MdePkg/Include/Protocol/StorageSecurityCommand.h
index 810af59b85..206ae79aff 100644
--- a/MdePkg/Include/Protocol/StorageSecurityCommand.h
+++ b/MdePkg/Include/Protocol/StorageSecurityCommand.h
@@ -59,7 +59,9 @@ typedef struct _EFI_STORAGE_SECURITY_COMMAND_PROTOCOL EFI_STORAGE_SECURITY_COMMA
   function shall return EFI_DEVICE_ERROR.
 
   @param  This                         Indicates a pointer to the calling context.
-  @param  MediaId                      ID of the medium to receive data from.
+  @param  MediaId                      ID of the medium to receive data from. If there is no
+                                       block IO protocol supported by the physical device, the
+                                       value of MediaId is undefined.
   @param  Timeout                      The timeout, in 100ns units, to use for the execution
                                        of the security protocol command. A Timeout value of 0
                                        means that this function will wait indefinitely for the
@@ -138,7 +140,9 @@ EFI_STATUS
   shall return EFI_DEVICE_ERROR.
 
   @param  This                         Indicates a pointer to the calling context.
-  @param  MediaId                      ID of the medium to receive data from.
+  @param  MediaId                      ID of the medium to receive data from. If there is no
+                                       block IO protocol supported by the physical device, the
+                                       value of MediaId is undefined.
   @param  Timeout                      The timeout, in 100ns units, to use for the execution
                                        of the security protocol command. A Timeout value of 0
                                        means that this function will wait indefinitely for the