diff --git a/lib/syntax_suggest/mini_stringio.rb b/lib/syntax_suggest/mini_stringio.rb
index ee5192ba90..2903275ea2 100644
--- a/lib/syntax_suggest/mini_stringio.rb
+++ b/lib/syntax_suggest/mini_stringio.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module SyntaxSuggest
   # Mini String IO [Private]
   #