diff --git a/osutils/data.go b/osutils/data.go
index b9fa4fc..ce8201b 100644
--- a/osutils/data.go
+++ b/osutils/data.go
@@ -29,5 +29,5 @@ func UuidValidate(uuid string) error {
 
 func isLetter(r rune) bool {
 	l := unicode.ToLower(r)
-	return (l >= 'a' && l <= 'z')
+	return (l >= 'a' && l <= 'f')
 }