diff --git a/lib/timeout.rb b/lib/timeout.rb
index e7b11c0..6a7f538 100644
--- a/lib/timeout.rb
+++ b/lib/timeout.rb
@@ -23,7 +23,7 @@
 # Copyright:: (C) 2000  Information-technology Promotion Agency, Japan
 
 module Timeout
-  VERSION = "0.1.1"
+  VERSION = "0.1.1".freeze
 
   # Raised by Timeout.timeout when the block times out.
   class Error < RuntimeError