diff --git a/Casks/thunderbird-beta.rb b/Casks/thunderbird-beta.rb
index 3b1e10572..bf121d261 100644
--- a/Casks/thunderbird-beta.rb
+++ b/Casks/thunderbird-beta.rb
@@ -1,10 +1,10 @@
 class ThunderbirdBeta < Cask
-  version '33.0b1'
-  sha256 '45549be5ddf4aaf7c50e08fa71dd8e5542cb36c8ca19498866cd0b8ebb3b6385'
+  version '34.0b1'
+  sha256 '775e548e592f2788d991fe41ff2093bc902ceaa19bef83429e613375c7fa7887'
 
   url "https://download-installer.cdn.mozilla.net/pub/thunderbird/releases/#{version}/mac/en-US/Thunderbird%20#{version}.dmg"
   homepage 'https://www.mozilla.org/en-US/thunderbird/all-beta.html'
-  license :oss
+  license :mpl
 
   app 'Thunderbird.app'
 end