diff --git a/Casks/kindlegen.rb b/Casks/kindlegen.rb
index 07b41b89f..66e9530be 100644
--- a/Casks/kindlegen.rb
+++ b/Casks/kindlegen.rb
@@ -4,6 +4,7 @@ class Kindlegen < Cask
 
   url "https://kindlegen.s3.amazonaws.com/KindleGen_Mac_i386_v#{version.gsub('.', '_')}.zip"
   homepage 'http://www.amazon.com/gp/feature.html?docId=1000765211'
+  license :unknown
 
   binary "KindleGen_Mac_i386_v#{version.gsub('.', '_')}/kindlegen"
 end