diff --git a/Casks/thunderbird-cn.rb b/Casks/thunderbird-cn.rb
index 8fca2cae7..92dac190e 100644
--- a/Casks/thunderbird-cn.rb
+++ b/Casks/thunderbird-cn.rb
@@ -4,6 +4,7 @@ class ThunderbirdCn < Cask
 
   url "http://ftp.mozilla.org/pub/mozilla.org/thunderbird/releases/#{version}/mac/zh-CN/Thunderbird%20#{version}.dmg"
   homepage 'https://www.mozilla.org/zh-CN/thunderbird/'
+  license :oss
 
   app 'Thunderbird.app'
 end