diff --git a/MdePkg/Include/Protocol/SimpleTextOut.h b/MdePkg/Include/Protocol/SimpleTextOut.h
index feff9a13dc..f8de06f665 100644
--- a/MdePkg/Include/Protocol/SimpleTextOut.h
+++ b/MdePkg/Include/Protocol/SimpleTextOut.h
@@ -392,6 +392,6 @@ struct _EFI_SIMPLE_TEXT_OUTPUT_PROTOCOL {
   EFI_SIMPLE_TEXT_OUTPUT_MODE   *Mode;
 };
 
-extern EFI_GUID gEfiSimpleTextOutputProtocolGuid;
+extern EFI_GUID gEfiSimpleTextOutProtocolGuid;
 
 #endif