diff --git a/FatPkg/EnhancedFatDxe/ReadWrite.c b/FatPkg/EnhancedFatDxe/ReadWrite.c
index 956db27a86..fb9e8026f1 100644
--- a/FatPkg/EnhancedFatDxe/ReadWrite.c
+++ b/FatPkg/EnhancedFatDxe/ReadWrite.c
@@ -117,7 +117,7 @@ Returns:
   //
   // Set the position
   //
-  if (Position == -1) {
+  if (Position == (UINT64)-1) {
     Position = OFile->FileSize;
   }
   //