diff --git a/Casks/bettertouchtool.rb b/Casks/bettertouchtool.rb
index ccee025eca8..a0af74a1eb6 100644
--- a/Casks/bettertouchtool.rb
+++ b/Casks/bettertouchtool.rb
@@ -5,6 +5,7 @@ class Bettertouchtool < Cask
   url 'http://www.boastr.de/BetterTouchTool.zip'
   appcast 'http://appcast.boastr.net'
   homepage 'http://blog.boastr.net/'
+  license :unknown
 
   app 'BetterTouchTool.app'
   zap :delete => [