diff --git a/Casks/webkit-nightly.rb b/Casks/webkit-nightly.rb
index 6a366d1df..6a987def4 100644
--- a/Casks/webkit-nightly.rb
+++ b/Casks/webkit-nightly.rb
@@ -4,6 +4,7 @@ class WebkitNightly < Cask
 
   url 'http://builds.nightly.webkit.org/files/trunk/mac/WebKit-SVN-r159487.dmg'
   homepage 'http://nightly.webkit.org/'
+  license :unknown
 
   app 'WebKit.app'
 end