diff --git a/lib/websocket/driver/hybi.rb b/lib/websocket/driver/hybi.rb
index 3540940..18951fb 100644
--- a/lib/websocket/driver/hybi.rb
+++ b/lib/websocket/driver/hybi.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: false
+
 module WebSocket
   class Driver
 
diff --git a/spec/websocket/driver/draft76_spec.rb b/spec/websocket/driver/draft76_spec.rb
index f9f3f1d..f834415 100644
--- a/spec/websocket/driver/draft76_spec.rb
+++ b/spec/websocket/driver/draft76_spec.rb
@@ -1,4 +1,5 @@
 # encoding=utf-8
+# frozen_string_literal: false
 
 require "spec_helper"