diff --git a/sample/pty/script.rb b/sample/pty/script.rb
index 903a6f75bd..c6659a4807 100644
--- a/sample/pty/script.rb
+++ b/sample/pty/script.rb
@@ -1,3 +1,4 @@
+# frozen_string_literal: true
 require 'pty'
 
 if ARGV.size == 0 then
@@ -34,4 +35,3 @@ PTY.spawn("/bin/csh") do |r_pty,w_pty,pid|
 end
 
 system "stty echo -raw lnext ^v"
-