diff --git a/EdkModulePkg/Library/EdkSerialPortLibNull/SerialPortLibNull.c b/EdkModulePkg/Library/EdkSerialPortLibNull/SerialPortLibNull.c
index af9b95705f..d6e91d687d 100644
--- a/EdkModulePkg/Library/EdkSerialPortLibNull/SerialPortLibNull.c
+++ b/EdkModulePkg/Library/EdkSerialPortLibNull/SerialPortLibNull.c
@@ -14,10 +14,12 @@
 
 **/
 
-/**
+/*
 
   Programmed hardware of Serial port.
 
+  @return    Always return EFI_UNSUPPORTED.
+
 **/
 EFI_STATUS
 EFIAPI