diff --git a/MdePkg/Library/UefiLib/UefiLib.c b/MdePkg/Library/UefiLib/UefiLib.c
index 835218f982..b6a33a0a48 100644
--- a/MdePkg/Library/UefiLib/UefiLib.c
+++ b/MdePkg/Library/UefiLib/UefiLib.c
@@ -839,7 +839,7 @@ LookupUnicodeString2 (
       SupportedLanguages += 3;
     }
   } else {
-    Found = !IsLanguageSupported(Language, SupportedLanguages);
+    Found = !IsLanguageSupported(SupportedLanguages, Language);
   }
 
 
@@ -1133,7 +1133,7 @@ AddUnicodeString2 (
       SupportedLanguages += 3;
     }
   } else {
-    Found = !IsLanguageSupported(Language, SupportedLanguages);
+    Found = !IsLanguageSupported(SupportedLanguages, Language);
   }
   //
   // If Language is not a member of SupportedLanguages, then return EFI_UNSUPPORTED