diff --git a/FatPkg/EnhancedFatDxe/FileName.c b/FatPkg/EnhancedFatDxe/FileName.c
index 4f73e9ef90..09690fb076 100644
--- a/FatPkg/EnhancedFatDxe/FileName.c
+++ b/FatPkg/EnhancedFatDxe/FileName.c
@@ -299,7 +299,7 @@ Returns:
 
 --*/
 {
-  CHAR16  Buffer[FAT_MAIN_NAME_LEN + 1];
+  CHAR16  Buffer[FAT_MAIN_NAME_LEN + 1 + FAT_EXTEND_NAME_LEN + 1];
   UINT8   OutCaseFlag;
 
   ASSERT (StrSize (Str) <= sizeof (Buffer));