diff --git a/lib/redmine/i18n.rb b/lib/redmine/i18n.rb
index dfeaf474e..44bad4d06 100644
--- a/lib/redmine/i18n.rb
+++ b/lib/redmine/i18n.rb
@@ -130,7 +130,7 @@ module Redmine
     end
 
     def find_language(lang)
-      @@languages_lookup = valid_languages.inject({}) {|k, v| k[v.to_s.downcase] = v; k }
+      @@languages_lookup ||= valid_languages.inject({}) {|k, v| k[v.to_s.downcase] = v; k }
       @@languages_lookup[lang.to_s.downcase]
     end