diff --git a/MdeModulePkg/Application/CapsuleApp/AppSupport.c b/MdeModulePkg/Application/CapsuleApp/AppSupport.c
index 6aea76a720..a5fd0ca316 100644
--- a/MdeModulePkg/Application/CapsuleApp/AppSupport.c
+++ b/MdeModulePkg/Application/CapsuleApp/AppSupport.c
@@ -74,7 +74,7 @@ GetArg (
 
 **/
 EFI_STATUS
-StrToBuf (
+InternalStrToBuf (
   OUT UINT8    *Buf,
   IN  UINTN    BufferLength,
   IN  CHAR16   *Str
@@ -135,7 +135,7 @@ StrToBuf (
 
 **/
 EFI_STATUS
-StrToGuid (
+InternalStrToGuid (
   IN  CHAR16   *Str,
   OUT EFI_GUID *Guid
   )
@@ -185,7 +185,7 @@ StrToGuid (
   //
   // Get the following 8 bytes data
   //
-  StrToBuf (&Guid->Data4[0], 2, Str);
+  InternalStrToBuf (&Guid->Data4[0], 2, Str);
   //
   // Skip 2 byte hex chars
   //
@@ -196,7 +196,7 @@ StrToGuid (
   } else {
     return EFI_UNSUPPORTED;
   }
-  StrToBuf (&Guid->Data4[2], 6, Str);
+  InternalStrToBuf (&Guid->Data4[2], 6, Str);
 
   return EFI_SUCCESS;
 }
diff --git a/MdeModulePkg/Application/CapsuleApp/CapsuleApp.c b/MdeModulePkg/Application/CapsuleApp/CapsuleApp.c
index 51372593de..5b8c147928 100644
--- a/MdeModulePkg/Application/CapsuleApp/CapsuleApp.c
+++ b/MdeModulePkg/Application/CapsuleApp/CapsuleApp.c
@@ -155,7 +155,7 @@ WriteFileFromBuffer (
 
 **/
 EFI_STATUS
-StrToGuid (
+InternalStrToGuid (
   IN  CHAR16   *Str,
   OUT EFI_GUID *Guid
   );
@@ -782,7 +782,7 @@ UefiMain (
         //
         // FMP->GetImage()
         //
-        Status = StrToGuid(Argv[3], &ImageTypeId);
+        Status = InternalStrToGuid(Argv[3], &ImageTypeId);
         if (EFI_ERROR(Status)) {
           Print (L"Invalid ImageTypeId - %s\n", Argv[3]);
           return Status;