diff --git a/MdePkg/Include/Library/UefiLib.h b/MdePkg/Include/Library/UefiLib.h
index 256498e3fd..bc2f712fdb 100644
--- a/MdePkg/Include/Library/UefiLib.h
+++ b/MdePkg/Include/Library/UefiLib.h
@@ -818,7 +818,7 @@ CHAR8 *
 EFIAPI
 GetBestLanguage (
   IN CONST CHAR8  *SupportedLanguages, 
-  IN BOOLEAN      Iso639Language,
+  IN UINTN        Iso639Language,
   ...
   );
 
diff --git a/MdePkg/Library/UefiLib/UefiLib.c b/MdePkg/Library/UefiLib/UefiLib.c
index ba449a1c34..23faa63226 100644
--- a/MdePkg/Library/UefiLib/UefiLib.c
+++ b/MdePkg/Library/UefiLib/UefiLib.c
@@ -1514,7 +1514,7 @@ CHAR8 *
 EFIAPI
 GetBestLanguage (
   IN CONST CHAR8  *SupportedLanguages, 
-  IN BOOLEAN      Iso639Language,
+  IN UINTN        Iso639Language,
   ...
   )
 {