diff --git a/Casks/firefoxnightly.rb b/Casks/firefoxnightly.rb
index f70a8514a..8344e3e05 100644
--- a/Casks/firefoxnightly.rb
+++ b/Casks/firefoxnightly.rb
@@ -1,5 +1,5 @@
 cask 'firefoxnightly' do
-  version '58.0a1'
+  version '59.0a1'
   sha256 :no_check # required as upstream package is updated in-place
 
   language 'cs' do