diff --git a/Casks/firefox-nightly.rb b/Casks/firefox-nightly.rb
index cfd30f0cc..5dfdaf9f8 100644
--- a/Casks/firefox-nightly.rb
+++ b/Casks/firefox-nightly.rb
@@ -1,7 +1,7 @@
 class FirefoxNightly < Cask
-  url 'http://ftp.mozilla.org/pub/mozilla.org/firefox/nightly/latest-trunk/firefox-30.0a1.en-US.mac.dmg'
+  url 'http://ftp.mozilla.org/pub/mozilla.org/firefox/nightly/latest-trunk/firefox-31.0a1.en-US.mac.dmg'
   homepage 'http://nightly.mozilla.org/'
-  version '30.0a1'
+  version '31.0a1'
   no_checksum
   link 'FirefoxNightly.app'
 end