diff --git a/Casks/kdiff3.rb b/Casks/kdiff3.rb
index 96c854ee9cd..1a4033582c2 100644
--- a/Casks/kdiff3.rb
+++ b/Casks/kdiff3.rb
@@ -5,6 +5,7 @@ class Kdiff3 < Cask
 
   url "https://downloads.sourceforge.net/project/kdiff3/kdiff3/#{version}/kdiff3-#{version}-MacOSX-64Bit.dmg"
   homepage 'http://kdiff3.sourceforge.net/'
+  license :oss
 
   app 'kdiff3.app'
   binary 'kdiff3.app/Contents/MacOS/kdiff3'