diff --git a/Casks/firefox-nightly-ja.rb b/Casks/firefoxnightly-ja.rb
similarity index 93%
rename from Casks/firefox-nightly-ja.rb
rename to Casks/firefoxnightly-ja.rb
index 9ad60c336..02413209e 100644
--- a/Casks/firefox-nightly-ja.rb
+++ b/Casks/firefoxnightly-ja.rb
@@ -1,4 +1,4 @@
-cask 'firefox-nightly-ja' do
+cask 'firefoxnightly-ja' do
   version '46.0a1'
   sha256 :no_check # required as upstream package is updated in-place